/*
 * externals.c :  routines dealing with (file) externals in the working copy
 *
 * ====================================================================
 *    Licensed to the Apache Software Foundation (ASF) under one
 *    or more contributor license agreements.  See the NOTICE file
 *    distributed with this work for additional information
 *    regarding copyright ownership.  The ASF licenses this file
 *    to you under the Apache License, Version 2.0 (the
 *    "License"); you may not use this file except in compliance
 *    with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing,
 *    software distributed under the License is distributed on an
 *    "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *    KIND, either express or implied.  See the License for the
 *    specific language governing permissions and limitations
 *    under the License.
 * ====================================================================
 */



#include <stdlib.h>
#include <string.h>

#include <apr_pools.h>
#include <apr_hash.h>
#include <apr_tables.h>
#include <apr_general.h>
#include <apr_uri.h>

#include "svn_dirent_uri.h"
#include "svn_path.h"
#include "svn_error.h"
#include "svn_hash.h"
#include "svn_io.h"
#include "svn_pools.h"
#include "svn_props.h"
#include "svn_string.h"
#include "svn_time.h"
#include "svn_types.h"
#include "svn_wc.h"

#include "private/svn_skel.h"
#include "private/svn_subr_private.h"

#include "wc.h"
#include "adm_files.h"
#include "props.h"
#include "translate.h"
#include "workqueue.h"
#include "conflicts.h"

#include "svn_private_config.h"

/** Externals **/

/*
 * Look for either
 *
 *   -r N
 *   -rN
 *
 * in the LINE_PARTS array and update the revision field in ITEM with
 * the revision if the revision is found.  Set REV_IDX to the index in
 * LINE_PARTS where the revision specification starts.  Remove from
 * LINE_PARTS the element(s) that specify the revision.
 * PARENT_DIRECTORY_DISPLAY and LINE are given to return a nice error
 * string.
 *
 * If this function returns successfully, then LINE_PARTS will have
 * only two elements in it.
 */
static svn_error_t *
find_and_remove_externals_revision(int *rev_idx,
                                   const char **line_parts,
                                   int num_line_parts,
                                   svn_wc_external_item2_t *item,
                                   const char *parent_directory_display,
                                   const char *line,
                                   apr_pool_t *pool)
{
  int i;

  for (i = 0; i < 2; ++i)
    {
      const char *token = line_parts[i];

      if (token[0] == '-' && token[1] == 'r')
        {
          svn_opt_revision_t end_revision = { svn_opt_revision_unspecified };
          const char *digits_ptr;
          int shift_count;
          int j;

          *rev_idx = i;

          if (token[2] == '\0')
            {
              /* There must be a total of four elements in the line if
                 -r N is used. */
              if (num_line_parts != 4)
                goto parse_error;

              shift_count = 2;
              digits_ptr = line_parts[i+1];
            }
          else
            {
              /* There must be a total of three elements in the line
                 if -rN is used. */
              if (num_line_parts != 3)
                goto parse_error;

              shift_count = 1;
              digits_ptr = token+2;
            }

          if (svn_opt_parse_revision(&item->revision,
                                     &end_revision,
                                     digits_ptr, pool) != 0)
            goto parse_error;
          /* We want a single revision, not a range. */
          if (end_revision.kind != svn_opt_revision_unspecified)
            goto parse_error;
          /* Allow only numbers and dates, not keywords. */
          if (item->revision.kind != svn_opt_revision_number
              && item->revision.kind != svn_opt_revision_date)
            goto parse_error;

          /* Shift any line elements past the revision specification
             down over the revision specification. */
          for (j = i; j < num_line_parts-shift_count; ++j)
            line_parts[j] = line_parts[j+shift_count];
          line_parts[num_line_parts-shift_count] = NULL;

          /* Found the revision, so leave the function immediately, do
           * not continue looking for additional revisions. */
          return SVN_NO_ERROR;
        }
    }

  /* No revision was found, so there must be exactly two items in the
     line array. */
  if (num_line_parts == 2)
    return SVN_NO_ERROR;

 parse_error:
  return svn_error_createf
    (SVN_ERR_CLIENT_INVALID_EXTERNALS_DESCRIPTION, NULL,
     _("Error parsing %s property on '%s': '%s'"),
     SVN_PROP_EXTERNALS,
     parent_directory_display,
     line);
}

svn_error_t *
svn_wc_parse_externals_description3(apr_array_header_t **externals_p,
                                    const char *parent_directory,
                                    const char *desc,
                                    svn_boolean_t canonicalize_url,
                                    apr_pool_t *pool)
{
  int i;
  apr_array_header_t *externals = NULL;
  apr_array_header_t *lines = svn_cstring_split(desc, "\n\r", TRUE, pool);
  const char *parent_directory_display = svn_path_is_url(parent_directory) ?
    parent_directory : svn_dirent_local_style(parent_directory, pool);

  /* If an error occurs halfway through parsing, *externals_p should stay
   * untouched. So, store the list in a local var first. */
  if (externals_p)
    externals = apr_array_make(pool, 1, sizeof(svn_wc_external_item2_t *));

  for (i = 0; i < lines->nelts; i++)
    {
      const char *line = APR_ARRAY_IDX(lines, i, const char *);
      apr_status_t status;
      char **line_parts;
      int num_line_parts;
      svn_wc_external_item2_t *item;
      const char *token0;
      const char *token1;
      svn_boolean_t token0_is_url;
      svn_boolean_t token1_is_url;

      /* Index into line_parts where the revision specification
         started. */
      int rev_idx = -1;

      if ((! line) || (line[0] == '#'))
        continue;

      /* else proceed */

      status = apr_tokenize_to_argv(line, &line_parts, pool);
      if (status)
        return svn_error_wrap_apr(status,
                                  _("Can't split line into components: '%s'"),
                                  line);
      /* Count the number of tokens. */
      for (num_line_parts = 0; line_parts[num_line_parts]; num_line_parts++)
        ;

      SVN_ERR(svn_wc_external_item2_create(&item, pool));
      item->revision.kind = svn_opt_revision_unspecified;
      item->peg_revision.kind = svn_opt_revision_unspecified;

      /*
       * There are six different formats of externals:
       *
       * 1) DIR URL
       * 2) DIR -r N URL
       * 3) DIR -rN  URL
       * 4) URL DIR
       * 5) -r N URL DIR
       * 6) -rN URL DIR
       *
       * The last three allow peg revisions in the URL.
       *
       * With relative URLs and no '-rN' or '-r N', there is no way to
       * distinguish between 'DIR URL' and 'URL DIR' when URL is a
       * relative URL like /svn/repos/trunk, so this case is taken as
       * case 4).
       */
      if (num_line_parts < 2 || num_line_parts > 4)
        return svn_error_createf
          (SVN_ERR_CLIENT_INVALID_EXTERNALS_DESCRIPTION, NULL,
           _("Error parsing %s property on '%s': '%s'"),
           SVN_PROP_EXTERNALS,
           parent_directory_display,
           line);

      /* To make it easy to check for the forms, find and remove -r N
         or -rN from the line item array.  If it is found, rev_idx
         contains the index into line_parts where '-r' was found and
         set item->revision to the parsed revision. */
      /* ### ugh. stupid cast. */
      SVN_ERR(find_and_remove_externals_revision(&rev_idx,
                                                 (const char **)line_parts,
                                                 num_line_parts, item,
                                                 parent_directory_display,
                                                 line, pool));

      token0 = line_parts[0];
      token1 = line_parts[1];

      token0_is_url = svn_path_is_url(token0);
      token1_is_url = svn_path_is_url(token1);

      if (token0_is_url && token1_is_url)
        return svn_error_createf
          (SVN_ERR_CLIENT_INVALID_EXTERNALS_DESCRIPTION, NULL,
           _("Invalid %s property on '%s': "
             "cannot use two absolute URLs ('%s' and '%s') in an external; "
             "one must be a path where an absolute or relative URL is "
             "checked out to"),
           SVN_PROP_EXTERNALS, parent_directory_display, token0, token1);

      if (0 == rev_idx && token1_is_url)
        return svn_error_createf
          (SVN_ERR_CLIENT_INVALID_EXTERNALS_DESCRIPTION, NULL,
           _("Invalid %s property on '%s': "
             "cannot use a URL '%s' as the target directory for an external "
             "definition"),
           SVN_PROP_EXTERNALS, parent_directory_display, token1);

      if (1 == rev_idx && token0_is_url)
        return svn_error_createf
          (SVN_ERR_CLIENT_INVALID_EXTERNALS_DESCRIPTION, NULL,
           _("Invalid %s property on '%s': "
             "cannot use a URL '%s' as the target directory for an external "
             "definition"),
           SVN_PROP_EXTERNALS, parent_directory_display, token0);

      /* The appearence of -r N or -rN forces the type of external.
         If -r is at the beginning of the line or the first token is
         an absolute URL or if the second token is not an absolute
         URL, then the URL supports peg revisions. */
      if (0 == rev_idx ||
          (-1 == rev_idx && (token0_is_url || ! token1_is_url)))
        {
          /* The URL is passed to svn_opt_parse_path in
             uncanonicalized form so that the scheme relative URL
             //hostname/foo is not collapsed to a server root relative
             URL /hostname/foo. */
          SVN_ERR(svn_opt_parse_path(&item->peg_revision, &item->url,
                                     token0, pool));
          item->target_dir = token1;
        }
      else
        {
          item->target_dir = token0;
          item->url = token1;
          item->peg_revision = item->revision;
        }

      SVN_ERR(svn_opt_resolve_revisions(&item->peg_revision,
                                        &item->revision, TRUE, FALSE,
                                        pool));

      item->target_dir = svn_dirent_internal_style(item->target_dir, pool);

      if (item->target_dir[0] == '\0'
          || svn_dirent_is_absolute(item->target_dir)
          || svn_path_is_backpath_present(item->target_dir)
          || !svn_dirent_skip_ancestor("dummy",
                                       svn_dirent_join("dummy",
                                                       item->target_dir,
                                                       pool)))
        return svn_error_createf
          (SVN_ERR_CLIENT_INVALID_EXTERNALS_DESCRIPTION, NULL,
           _("Invalid %s property on '%s': "
             "target '%s' is an absolute path or involves '..'"),
           SVN_PROP_EXTERNALS,
           parent_directory_display,
           item->target_dir);

      if (canonicalize_url)
        {
          /* Uh... this is stupid.  But it's consistent with what our
             code did before we split up the relpath/dirent/uri APIs.
             Still, given this, it's no wonder that our own libraries
             don't ask this function to canonicalize the results.  */
          if (svn_path_is_url(item->url))
            item->url = svn_uri_canonicalize(item->url, pool);
          else
            item->url = svn_dirent_canonicalize(item->url, pool);
        }

      if (externals)
        APR_ARRAY_PUSH(externals, svn_wc_external_item2_t *) = item;
    }

  if (externals_p)
    *externals_p = externals;

  return SVN_NO_ERROR;
}

svn_error_t *
svn_wc__externals_find_target_dups(apr_array_header_t **duplicate_targets,
                                   apr_array_header_t *externals,
                                   apr_pool_t *pool,
                                   apr_pool_t *scratch_pool)
{
  int i;
  unsigned int len;
  unsigned int len2;
  const char *target;
  apr_hash_t *targets = apr_hash_make(scratch_pool);
  apr_hash_t *targets2 = NULL;
  *duplicate_targets = NULL;

  for (i = 0; i < externals->nelts; i++)
    {
      target = APR_ARRAY_IDX(externals, i,
                                         svn_wc_external_item2_t*)->target_dir;
      len = apr_hash_count(targets);
      svn_hash_sets(targets, target, "");
      if (len == apr_hash_count(targets))
        {
          /* Hashtable length is unchanged. This must be a duplicate. */

          /* Collapse multiple duplicates of the same target by using a second
           * hash layer. */
          if (! targets2)
            targets2 = apr_hash_make(scratch_pool);
          len2 = apr_hash_count(targets2);
          svn_hash_sets(targets2, target, "");
          if (len2 < apr_hash_count(targets2))
            {
              /* The second hash list just got bigger, i.e. this target has
               * not been counted as duplicate before. */
              if (! *duplicate_targets)
                {
                  *duplicate_targets = apr_array_make(
                                    pool, 1, sizeof(svn_wc_external_item2_t*));
                }
              APR_ARRAY_PUSH((*duplicate_targets), const char *) = target;
            }
          /* Else, this same target has already been recorded as a duplicate,
           * don't count it again. */
        }
    }
  return SVN_NO_ERROR;
}

struct edit_baton
{
  apr_pool_t *pool;
  svn_wc__db_t *db;

  /* We explicitly use wri_abspath and local_abspath here, because we
     might want to install file externals in an obstructing working copy */
  const char *wri_abspath;     /* The working defining the file external */
  const char *local_abspath;   /* The file external itself */
  const char *name;            /* The basename of the file external itself */

  /* Information from the caller */
  svn_boolean_t use_commit_times;
  const apr_array_header_t *ext_patterns;
  const char *diff3cmd;

  const char *repos_root_url;
  const char *repos_uuid;
  const char *old_repos_relpath;
  const char *new_repos_relpath;

  const char *record_ancestor_abspath;
  const char *recorded_repos_relpath;
  svn_revnum_t recorded_peg_revision;
  svn_revnum_t recorded_revision;

  /* Introducing a new file external */
  svn_boolean_t added;

  svn_wc_conflict_resolver_func2_t conflict_func;
  void *conflict_baton;
  svn_cancel_func_t cancel_func;
  void *cancel_baton;
  svn_wc_notify_func2_t notify_func;
  void *notify_baton;

  svn_revnum_t *target_revision;

  /* What was there before the update */
  svn_revnum_t original_revision;
  const svn_checksum_t *original_checksum;

  /* What we are installing now */
  const char *new_pristine_abspath;
  svn_checksum_t *new_sha1_checksum;
  svn_checksum_t *new_md5_checksum;

  /* List of incoming propchanges */
  apr_array_header_t *propchanges;

  /* Array of svn_prop_inherited_item_t * structures representing the
     properties inherited by the base node at LOCAL_ABSPATH. */
  apr_array_header_t *iprops;

  /* The last change information */
  svn_revnum_t changed_rev;
  apr_time_t changed_date;
  const char *changed_author;

  svn_boolean_t had_props;

  svn_boolean_t file_closed;
};

/* svn_delta_editor_t function for svn_wc__get_file_external_editor */
static svn_error_t *
set_target_revision(void *edit_baton,
                     svn_revnum_t target_revision,
                     apr_pool_t *pool)
{
  struct edit_baton *eb = edit_baton;

  *eb->target_revision = target_revision;

  return SVN_NO_ERROR;
}

/* svn_delta_editor_t function for svn_wc__get_file_external_editor */
static svn_error_t *
open_root(void *edit_baton,
          svn_revnum_t base_revision,
          apr_pool_t *dir_pool,
          void **root_baton)
{
  *root_baton = edit_baton;
  return SVN_NO_ERROR;
}

/* svn_delta_editor_t function for svn_wc__get_file_external_editor */
static svn_error_t *
add_file(const char *path,
         void *parent_baton,
         const char *copyfrom_path,
         svn_revnum_t copyfrom_revision,
         apr_pool_t *file_pool,
         void **file_baton)
{
  struct edit_baton *eb = parent_baton;
  if (strcmp(path, eb->name))
      return svn_error_createf(SVN_ERR_WC_PATH_NOT_FOUND, NULL,
                               _("This editor can only update '%s'"),
                               svn_dirent_local_style(eb->local_abspath,
                                                      file_pool));

  *file_baton = eb;
  eb->original_revision = SVN_INVALID_REVNUM;
  eb->added = TRUE;

  return SVN_NO_ERROR;
}

/* svn_delta_editor_t function for svn_wc__get_file_external_editor */
static svn_error_t *
open_file(const char *path,
          void *parent_baton,
          svn_revnum_t base_revision,
          apr_pool_t *file_pool,
          void **file_baton)
{
  struct edit_baton *eb = parent_baton;
  svn_node_kind_t kind;
  if (strcmp(path, eb->name))
      return svn_error_createf(SVN_ERR_WC_PATH_NOT_FOUND, NULL,
                               _("This editor can only update '%s'"),
                               svn_dirent_local_style(eb->local_abspath,
                                                      file_pool));

  *file_baton = eb;
  SVN_ERR(svn_wc__db_base_get_info(NULL, &kind, &eb->original_revision,
                                   &eb->old_repos_relpath, NULL, NULL,
                                   &eb->changed_rev,
                                   &eb->changed_date, &eb->changed_author,
                                   NULL, &eb->original_checksum, NULL, NULL,
                                   &eb->had_props, NULL, NULL,
                                   eb->db, eb->local_abspath,
                                   eb->pool, file_pool));

  if (kind != svn_node_file)
    return svn_error_createf(SVN_ERR_WC_PATH_UNEXPECTED_STATUS, NULL,
                               _("Node '%s' is no existing file external"),
                               svn_dirent_local_style(eb->local_abspath,
                                                      file_pool));
  return SVN_NO_ERROR;
}

/* svn_delta_editor_t function for svn_wc__get_file_external_editor */
static svn_error_t *
apply_textdelta(void *file_baton,
                const char *base_checksum_digest,
                apr_pool_t *pool,
                svn_txdelta_window_handler_t *handler,
                void **handler_baton)
{
  struct edit_baton *eb = file_baton;
  svn_stream_t *src_stream;
  svn_stream_t *dest_stream;

  if (eb->original_checksum)
    {
      if (base_checksum_digest)
        {
          svn_checksum_t *expected_checksum;
          const svn_checksum_t *original_md5;

          SVN_ERR(svn_checksum_parse_hex(&expected_checksum, svn_checksum_md5,
                                         base_checksum_digest, pool));

          if (eb->original_checksum->kind != svn_checksum_md5)
            SVN_ERR(svn_wc__db_pristine_get_md5(&original_md5,
                                                eb->db, eb->wri_abspath,
                                                eb->original_checksum,
                                                pool, pool));
          else
            original_md5 = eb->original_checksum;

          if (!svn_checksum_match(expected_checksum, original_md5))
            return svn_error_trace(svn_checksum_mismatch_err(
                                    expected_checksum,
                                    original_md5,
                                    pool,
                                    _("Base checksum mismatch for '%s'"),
                                    svn_dirent_local_style(eb->local_abspath,
                                                           pool)));
        }

      SVN_ERR(svn_wc__db_pristine_read(&src_stream, NULL, eb->db,
                                       eb->wri_abspath, eb->original_checksum,
                                       pool, pool));
    }
  else
    src_stream = svn_stream_empty(pool);

  SVN_ERR(svn_wc__open_writable_base(&dest_stream, &eb->new_pristine_abspath,
                                     &eb->new_md5_checksum,
                                     &eb->new_sha1_checksum,
                                     eb->db, eb->wri_abspath,
                                     eb->pool, pool));

  svn_txdelta_apply(src_stream, dest_stream, NULL, eb->local_abspath, pool,
                    handler, handler_baton);

  return SVN_NO_ERROR;
}

/* svn_delta_editor_t function for svn_wc__get_file_external_editor */
static svn_error_t *
change_file_prop(void *file_baton,
                 const char *name,
                 const svn_string_t *value,
                 apr_pool_t *pool)
{
  struct edit_baton *eb = file_baton;
  svn_prop_t *propchange;

  propchange = apr_array_push(eb->propchanges);
  propchange->name = apr_pstrdup(eb->pool, name);
  propchange->value = value ? svn_string_dup(value, eb->pool) : NULL;

  return SVN_NO_ERROR;
}

/* svn_delta_editor_t function for svn_wc__get_file_external_editor */
static svn_error_t *
close_file(void *file_baton,
           const char *expected_md5_digest,
           apr_pool_t *pool)
{
  struct edit_baton *eb = file_baton;
  svn_wc_notify_state_t prop_state = svn_wc_notify_state_unknown;
  svn_wc_notify_state_t content_state = svn_wc_notify_state_unknown;
  svn_boolean_t obstructed = FALSE;

  eb->file_closed = TRUE; /* We bump the revision here */

  /* Check the checksum, if provided */
  if (expected_md5_digest)
    {
      svn_checksum_t *expected_md5_checksum;
      const svn_checksum_t *actual_md5_checksum = eb->new_md5_checksum;

      SVN_ERR(svn_checksum_parse_hex(&expected_md5_checksum, svn_checksum_md5,
                                     expected_md5_digest, pool));

      if (actual_md5_checksum == NULL)
        {
          actual_md5_checksum = eb->original_checksum;

          if (actual_md5_checksum != NULL
              && actual_md5_checksum->kind != svn_checksum_md5)
            {
              SVN_ERR(svn_wc__db_pristine_get_md5(&actual_md5_checksum,
                                                  eb->db, eb->wri_abspath,
                                                  actual_md5_checksum,
                                                  pool, pool));
            }
        }

      if (! svn_checksum_match(expected_md5_checksum, actual_md5_checksum))
        return svn_checksum_mismatch_err(
                        expected_md5_checksum,
                        actual_md5_checksum, pool,
                        _("Checksum mismatch for '%s'"),
                        svn_dirent_local_style(eb->local_abspath, pool));
    }

  /* First move the file in the pristine store; this hands over the cleanup
     behavior to the pristine store. */
  if (eb->new_sha1_checksum)
    {
      SVN_ERR(svn_wc__db_pristine_install(eb->db, eb->new_pristine_abspath,
                                          eb->new_sha1_checksum,
                                          eb->new_md5_checksum, pool));

      eb->new_pristine_abspath = NULL;
    }

  /* Merge the changes */
  {
    svn_skel_t *all_work_items = NULL;
    svn_skel_t *conflict_skel = NULL;
    svn_skel_t *work_item;
    apr_hash_t *base_props = NULL;
    apr_hash_t *actual_props = NULL;
    apr_hash_t *new_pristine_props = NULL;
    apr_hash_t *new_actual_props = NULL;
    apr_hash_t *new_dav_props = NULL;
    const svn_checksum_t *new_checksum = NULL;
    const svn_checksum_t *original_checksum = NULL;

    svn_boolean_t added = !SVN_IS_VALID_REVNUM(eb->original_revision);

    if (! added)
      {
        new_checksum = eb->original_checksum;

        if (eb->had_props)
          SVN_ERR(svn_wc__db_base_get_props(
                    &base_props, eb->db, eb->local_abspath, pool, pool));

        SVN_ERR(svn_wc__db_read_props(
                  &actual_props, eb->db, eb->local_abspath, pool, pool));
      }

    if (!base_props)
      base_props = apr_hash_make(pool);

    if (!actual_props)
      actual_props = apr_hash_make(pool);

    if (eb->new_sha1_checksum)
      new_checksum = eb->new_sha1_checksum;

    /* Merge the properties */
    {
      apr_array_header_t *entry_prop_changes;
      apr_array_header_t *dav_prop_changes;
      apr_array_header_t *regular_prop_changes;
      int i;

      SVN_ERR(svn_categorize_props(eb->propchanges, &entry_prop_changes,
                                   &dav_prop_changes, &regular_prop_changes,
                                   pool));

      /* Read the entry-prop changes to update the last-changed info. */
      for (i = 0; i < entry_prop_changes->nelts; i++)
        {
          const svn_prop_t *prop = &APR_ARRAY_IDX(entry_prop_changes, i,
                                                  svn_prop_t);

          if (! prop->value)
            continue; /* authz or something */

          if (! strcmp(prop->name, SVN_PROP_ENTRY_LAST_AUTHOR))
            eb->changed_author = apr_pstrdup(pool, prop->value->data);
          else if (! strcmp(prop->name, SVN_PROP_ENTRY_COMMITTED_REV))
            {
              apr_int64_t rev;
              SVN_ERR(svn_cstring_atoi64(&rev, prop->value->data));
              eb->changed_rev = (svn_revnum_t)rev;
            }
          else if (! strcmp(prop->name, SVN_PROP_ENTRY_COMMITTED_DATE))
            SVN_ERR(svn_time_from_cstring(&eb->changed_date, prop->value->data,
                                          pool));
        }

      /* Store the DAV-prop (aka WC-prop) changes.  (This treats a list
       * of changes as a list of new props, but we only use this when
       * adding a new file and it's equivalent in that case.) */
      if (dav_prop_changes->nelts > 0)
        new_dav_props = svn_prop_array_to_hash(dav_prop_changes, pool);

      /* Merge the regular prop changes. */
      if (regular_prop_changes->nelts > 0)
        {
          new_pristine_props = svn_prop__patch(base_props, regular_prop_changes,
                                               pool);
          SVN_ERR(svn_wc__merge_props(&conflict_skel,
                                      &prop_state,
                                      &new_actual_props,
                                      eb->db, eb->local_abspath,
                                      NULL /* server_baseprops*/,
                                      base_props,
                                      actual_props,
                                      regular_prop_changes,
                                      pool, pool));
        }
      else
        {
          new_pristine_props = base_props;
          new_actual_props = actual_props;
        }
    }

    /* Merge the text */
    if (eb->new_sha1_checksum)
      {
        svn_node_kind_t disk_kind;
        svn_boolean_t install_pristine = FALSE;
        const char *install_from = NULL;

        SVN_ERR(svn_io_check_path(eb->local_abspath, &disk_kind, pool));

        if (disk_kind == svn_node_none)
          {
            /* Just install the file */
            install_pristine = TRUE;
            content_state = svn_wc_notify_state_changed;
          }
        else if (disk_kind != svn_node_file
                 || (eb->added && disk_kind == svn_node_file))
          {
            /* The node is obstructed; we just change the DB */
            obstructed = TRUE;
            content_state = svn_wc_notify_state_unchanged;
          }
        else
          {
            svn_boolean_t is_mod;
            SVN_ERR(svn_wc__internal_file_modified_p(&is_mod,
                                                     eb->db, eb->local_abspath,
                                                     FALSE, pool));

            if (!is_mod)
              {
                install_pristine = TRUE;
                content_state = svn_wc_notify_state_changed;
              }
            else
              {
                svn_boolean_t found_text_conflict;

                /* Ok, we have to do some work to merge a local change */
                SVN_ERR(svn_wc__perform_file_merge(&work_item,
                                                   &conflict_skel,
                                                   &found_text_conflict,
                                                   eb->db,
                                                   eb->local_abspath,
                                                   eb->wri_abspath,
                                                   new_checksum,
                                                   original_checksum,
                                                   actual_props,
                                                   eb->ext_patterns,
                                                   eb->original_revision,
                                                   *eb->target_revision,
                                                   eb->propchanges,
                                                   eb->diff3cmd,
                                                   eb->cancel_func,
                                                   eb->cancel_baton,
                                                   pool, pool));

                all_work_items = svn_wc__wq_merge(all_work_items, work_item,
                                                  pool);

                if (found_text_conflict)
                  content_state = svn_wc_notify_state_conflicted;
                else
                  content_state = svn_wc_notify_state_merged;
              }
          }
        if (install_pristine)
          {
            SVN_ERR(svn_wc__wq_build_file_install(&work_item, eb->db,
                                            eb->local_abspath,
                                            install_from,
                                            eb->use_commit_times, TRUE,
                                            pool, pool));

            all_work_items = svn_wc__wq_merge(all_work_items, work_item, pool);
          }
      }
    else
      {
        content_state = svn_wc_notify_state_unchanged;
        /* ### Retranslate on magic property changes, etc. */
      }

    /* Generate a conflict description, if needed */
    if (conflict_skel)
      {
        SVN_ERR(svn_wc__conflict_skel_set_op_switch(
                            conflict_skel,
                            svn_wc_conflict_version_create2(
                                    eb->repos_root_url,
                                    eb->repos_uuid,
                                    eb->old_repos_relpath,
                                    eb->original_revision,
                                    svn_node_file,
                                    pool),
                            svn_wc_conflict_version_create2(
                                    eb->repos_root_url,
                                    eb->repos_uuid,
                                    eb->new_repos_relpath,
                                    *eb->target_revision,
                                    svn_node_file,
                                    pool),
                            pool, pool));
        SVN_ERR(svn_wc__conflict_create_markers(&work_item,
                                                eb->db, eb->local_abspath,
                                                conflict_skel,
                                                pool, pool));
        all_work_items = svn_wc__wq_merge(all_work_items, work_item,
                                          pool);
      }

    /* Install the file in the DB */
    SVN_ERR(svn_wc__db_external_add_file(
                        eb->db,
                        eb->local_abspath,
                        eb->wri_abspath,
                        eb->new_repos_relpath,
                        eb->repos_root_url,
                        eb->repos_uuid,
                        *eb->target_revision,
                        new_pristine_props,
                        eb->iprops,
                        eb->changed_rev,
                        eb->changed_date,
                        eb->changed_author,
                        new_checksum,
                        new_dav_props,
                        eb->record_ancestor_abspath,
                        eb->recorded_repos_relpath,
                        eb->recorded_peg_revision,
                        eb->recorded_revision,
                        TRUE, new_actual_props,
                        FALSE /* keep_recorded_info */,
                        conflict_skel,
                        all_work_items,
                        pool));

    /* close_edit may also update iprops for switched files, catching
       those for which close_file is never called (e.g. an update of a
       file external with no changes).  So as a minor optimization we
       clear the iprops so as not to set them again in close_edit. */
    eb->iprops = NULL;

    /* Run the work queue to complete the installation */
    SVN_ERR(svn_wc__wq_run(eb->db, eb->wri_abspath,
                           eb->cancel_func, eb->cancel_baton, pool));
  }

  /* Notify */
  if (eb->notify_func)
    {
      svn_wc_notify_action_t action;
      svn_wc_notify_t *notify;

      if (!eb->added)
        action = obstructed ? svn_wc_notify_update_shadowed_update
                            : svn_wc_notify_update_update;
      else
        action = obstructed ? svn_wc_notify_update_shadowed_add
                            : svn_wc_notify_update_add;

      notify = svn_wc_create_notify(eb->local_abspath, action, pool);
      notify->kind = svn_node_file;

      notify->revision = *eb->target_revision;
      notify->prop_state = prop_state;
      notify->content_state = content_state;

      notify->old_revision = eb->original_revision;

      eb->notify_func(eb->notify_baton, notify, pool);
    }

  return SVN_NO_ERROR;
}

/* svn_delta_editor_t function for svn_wc__get_file_external_editor */
static svn_error_t *
close_edit(void *edit_baton,
           apr_pool_t *pool)
{
  struct edit_baton *eb = edit_baton;

  if (!eb->file_closed)
    {
      apr_hash_t *wcroot_iprops = NULL;
      /* The file wasn't updated, but its url or revision might have...
         e.g. switch between branches for relative externals.

         Just bump the information as that is just as expensive as
         investigating when we should and shouldn't update it...
         and avoid hard to debug edge cases */

      if (eb->iprops)
        {
          wcroot_iprops = apr_hash_make(pool);
          svn_hash_sets(wcroot_iprops, eb->local_abspath, eb->iprops);
        }

      SVN_ERR(svn_wc__db_op_bump_revisions_post_update(eb->db,
                                                       eb->local_abspath,
                                                       svn_depth_infinity,
                                                       eb->new_repos_relpath,
                                                       eb->repos_root_url,
                                                       eb->repos_uuid,
                                                       *eb->target_revision,
                                                       apr_hash_make(pool)
                                                       /* exclude_relpaths */,
                                                       wcroot_iprops,
                                                       eb->notify_func,
                                                       eb->notify_baton,
                                                       pool));
    }

  return SVN_NO_ERROR;
}

svn_error_t *
svn_wc__get_file_external_editor(const svn_delta_editor_t **editor,
                                 void **edit_baton,
                                 svn_revnum_t *target_revision,
                                 svn_wc_context_t *wc_ctx,
                                 const char *local_abspath,
                                 const char *wri_abspath,
                                 const char *url,
                                 const char *repos_root_url,
                                 const char *repos_uuid,
                                 apr_array_header_t *iprops,
                                 svn_boolean_t use_commit_times,
                                 const char *diff3_cmd,
                                 const apr_array_header_t *preserved_exts,
                                 const char *record_ancestor_abspath,
                                 const char *recorded_url,
                                 const svn_opt_revision_t *recorded_peg_rev,
                                 const svn_opt_revision_t *recorded_rev,
                                 svn_wc_conflict_resolver_func2_t conflict_func,
                                 void *conflict_baton,
                                 svn_cancel_func_t cancel_func,
                                 void *cancel_baton,
                                 svn_wc_notify_func2_t notify_func,
                                 void *notify_baton,
                                 apr_pool_t *result_pool,
                                 apr_pool_t *scratch_pool)
{
  svn_wc__db_t *db = wc_ctx->db;
  apr_pool_t *edit_pool = result_pool;
  struct edit_baton *eb = apr_pcalloc(edit_pool, sizeof(*eb));
  svn_delta_editor_t *tree_editor = svn_delta_default_editor(edit_pool);

  eb->pool = edit_pool;
  eb->db = db;
  eb->local_abspath = apr_pstrdup(edit_pool, local_abspath);
  if (wri_abspath)
    eb->wri_abspath = apr_pstrdup(edit_pool, wri_abspath);
  else
    eb->wri_abspath = svn_dirent_dirname(local_abspath, edit_pool);
  eb->name = svn_dirent_basename(eb->local_abspath, NULL);
  eb->target_revision = target_revision;

  eb->repos_root_url = apr_pstrdup(edit_pool, repos_root_url);
  eb->repos_uuid = apr_pstrdup(edit_pool, repos_uuid);
  eb->new_repos_relpath = svn_uri_skip_ancestor(eb->repos_root_url, url, edit_pool);
  eb->old_repos_relpath = eb->new_repos_relpath;

  eb->original_revision = SVN_INVALID_REVNUM;

  eb->iprops = iprops;

  eb->use_commit_times = use_commit_times;
  eb->ext_patterns = preserved_exts;
  eb->diff3cmd = diff3_cmd;

  eb->record_ancestor_abspath = apr_pstrdup(edit_pool,record_ancestor_abspath);
  eb->recorded_repos_relpath = svn_uri_skip_ancestor(repos_root_url, recorded_url,
                                                     edit_pool);

  eb->changed_rev = SVN_INVALID_REVNUM;

  if (recorded_peg_rev->kind == svn_opt_revision_number)
    eb->recorded_peg_revision = recorded_peg_rev->value.number;
  else
    eb->recorded_peg_revision = SVN_INVALID_REVNUM; /* Not fixed/HEAD */

  if (recorded_rev->kind == svn_opt_revision_number)
    eb->recorded_revision = recorded_rev->value.number;
  else
    eb->recorded_revision = SVN_INVALID_REVNUM; /* Not fixed/HEAD */

  eb->conflict_func = conflict_func;
  eb->conflict_baton = conflict_baton;
  eb->cancel_func = cancel_func;
  eb->cancel_baton = cancel_baton;
  eb->notify_func = notify_func;
  eb->notify_baton = notify_baton;

  eb->propchanges  = apr_array_make(edit_pool, 1, sizeof(svn_prop_t));

  tree_editor->open_root = open_root;
  tree_editor->set_target_revision = set_target_revision;
  tree_editor->add_file = add_file;
  tree_editor->open_file = open_file;
  tree_editor->apply_textdelta = apply_textdelta;
  tree_editor->change_file_prop = change_file_prop;
  tree_editor->close_file = close_file;
  tree_editor->close_edit = close_edit;

  return svn_delta_get_cancellation_editor(cancel_func, cancel_baton,
                                           tree_editor, eb,
                                           editor, edit_baton,
                                           result_pool);
}

svn_error_t *
svn_wc__crawl_file_external(svn_wc_context_t *wc_ctx,
                            const char *local_abspath,
                            const svn_ra_reporter3_t *reporter,
                            void *report_baton,
                            svn_boolean_t restore_files,
                            svn_boolean_t use_commit_times,
                            svn_cancel_func_t cancel_func,
                            void *cancel_baton,
                            svn_wc_notify_func2_t notify_func,
                            void *notify_baton,
                            apr_pool_t *scratch_pool)
{
  svn_wc__db_t *db = wc_ctx->db;
  svn_error_t *err;
  svn_node_kind_t kind;
  svn_wc__db_lock_t *lock;
  svn_revnum_t revision;
  const char *repos_root_url;
  const char *repos_relpath;
  svn_boolean_t update_root;

  err = svn_wc__db_base_get_info(NULL, &kind, &revision,
                                 &repos_relpath, &repos_root_url, NULL, NULL,
                                 NULL, NULL, NULL, NULL, NULL, &lock,
                                 NULL, NULL, &update_root,
                                 db, local_abspath,
                                 scratch_pool, scratch_pool);

  if (err
      || kind == svn_node_dir
      || !update_root)
    {
      if (err && err->apr_err != SVN_ERR_WC_PATH_NOT_FOUND)
        return svn_error_trace(err);

      svn_error_clear(err);

      /* We don't know about this node, so all we have to do is tell
         the reporter that we don't know this node.

         But first we have to start the report by sending some basic
         information for the root. */

      SVN_ERR(reporter->set_path(report_baton, "", 0, svn_depth_infinity,
                                 FALSE, NULL, scratch_pool));
      SVN_ERR(reporter->delete_path(report_baton, "", scratch_pool));

      /* Finish the report, which causes the update editor to be
         driven. */
      SVN_ERR(reporter->finish_report(report_baton, scratch_pool));

      return SVN_NO_ERROR;
    }
  else
    {
      if (restore_files)
        {
          svn_node_kind_t disk_kind;
          SVN_ERR(svn_io_check_path(local_abspath, &disk_kind, scratch_pool));

          if (disk_kind == svn_node_none)
            {
              err = svn_wc_restore(wc_ctx, local_abspath, use_commit_times,
                                   scratch_pool);

              if (err)
                {
                  if (err->apr_err != SVN_ERR_WC_PATH_UNEXPECTED_STATUS)
                    return svn_error_trace(err);

                  svn_error_clear(err);
                }
            }
        }

      /* Report that we know the path */
      SVN_ERR(reporter->set_path(report_baton, "", revision,
                                 svn_depth_infinity, FALSE, NULL,
                                 scratch_pool));

      /* For compatibility with the normal update editor report we report
         the target as switched.

         ### We can probably report a parent url and unswitched later */
      SVN_ERR(reporter->link_path(report_baton, "",
                                  svn_path_url_add_component2(repos_root_url,
                                                              repos_relpath,
                                                              scratch_pool),
                                  revision,
                                  svn_depth_infinity,
                                  FALSE /* start_empty*/,
                                  lock ? lock->token : NULL,
                                  scratch_pool));
    }

  return svn_error_trace(reporter->finish_report(report_baton, scratch_pool));
}

svn_error_t *
svn_wc__read_external_info(svn_node_kind_t *external_kind,
                           const char **defining_abspath,
                           const char **defining_url,
                           svn_revnum_t *defining_operational_revision,
                           svn_revnum_t *defining_revision,
                           svn_wc_context_t *wc_ctx,
                           const char *wri_abspath,
                           const char *local_abspath,
                           svn_boolean_t ignore_enoent,
                           apr_pool_t *result_pool,
                           apr_pool_t *scratch_pool)
{
  const char *repos_root_url;
  svn_wc__db_status_t status;
  svn_node_kind_t kind;
  svn_error_t *err;

  err = svn_wc__db_external_read(&status, &kind, defining_abspath,
                                 defining_url ? &repos_root_url : NULL, NULL,
                                 defining_url, defining_operational_revision,
                                 defining_revision,
                                 wc_ctx->db, local_abspath, wri_abspath,
                                 result_pool, scratch_pool);

  if (err)
    {
      if (err->apr_err != SVN_ERR_WC_PATH_NOT_FOUND || !ignore_enoent)
        return svn_error_trace(err);

      svn_error_clear(err);

      if (external_kind)
        *external_kind = svn_node_none;

      if (defining_abspath)
        *defining_abspath = NULL;

      if (defining_url)
        *defining_url = NULL;

      if (defining_operational_revision)
        *defining_operational_revision = SVN_INVALID_REVNUM;

      if (defining_revision)
        *defining_revision = SVN_INVALID_REVNUM;

      return SVN_NO_ERROR;
    }

  if (external_kind)
    {
      if (status != svn_wc__db_status_normal)
        *external_kind = svn_node_unknown;
      else
        switch(kind)
          {
            case svn_node_file:
            case svn_node_symlink:
              *external_kind = svn_node_file;
              break;
            case svn_node_dir:
              *external_kind = svn_node_dir;
              break;
            default:
              *external_kind = svn_node_none;
          }
    }

  if (defining_url && *defining_url)
    *defining_url = svn_path_url_add_component2(repos_root_url, *defining_url,
                                                result_pool);

  return SVN_NO_ERROR;
}

/* Return TRUE in *IS_ROLLED_OUT iff a node exists at XINFO->LOCAL_ABSPATH and
 * if that node's origin corresponds with XINFO->REPOS_ROOT_URL and
 * XINFO->REPOS_RELPATH.  All allocations are made in SCRATCH_POOL. */
static svn_error_t *
is_external_rolled_out(svn_boolean_t *is_rolled_out,
                       svn_wc_context_t *wc_ctx,
                       svn_wc__committable_external_info_t *xinfo,
                       apr_pool_t *scratch_pool)
{
  const char *repos_relpath;
  const char *repos_root_url;
  svn_error_t *err;

  *is_rolled_out = FALSE;

  err = svn_wc__db_base_get_info(NULL, NULL, NULL, &repos_relpath,
                                 &repos_root_url, NULL, NULL, NULL, NULL,
                                 NULL, NULL, NULL, NULL, NULL, NULL, NULL,
                                 wc_ctx->db, xinfo->local_abspath,
                                 scratch_pool, scratch_pool);

  if (err)
    {
      if (err->apr_err == SVN_ERR_WC_PATH_NOT_FOUND)
        {
          svn_error_clear(err);
          return SVN_NO_ERROR;
        }
      SVN_ERR(err);
    }

  *is_rolled_out = (strcmp(xinfo->repos_root_url, repos_root_url) == 0 &&
                    strcmp(xinfo->repos_relpath, repos_relpath) == 0);
  return SVN_NO_ERROR;
}

svn_error_t *
svn_wc__committable_externals_below(apr_array_header_t **externals,
                                    svn_wc_context_t *wc_ctx,
                                    const char *local_abspath,
                                    svn_depth_t depth,
                                    apr_pool_t *result_pool,
                                    apr_pool_t *scratch_pool)
{
  apr_array_header_t *orig_externals;
  int i;
  apr_pool_t *iterpool;

  /* For svn_depth_files, this also fetches dirs. They are filtered later. */
  SVN_ERR(svn_wc__db_committable_externals_below(&orig_externals,
                                                 wc_ctx->db,
                                                 local_abspath,
                                                 depth != svn_depth_infinity,
                                                 result_pool, scratch_pool));

  if (orig_externals == NULL)
    return SVN_NO_ERROR;

  iterpool = svn_pool_create(scratch_pool);

  for (i = 0; i < orig_externals->nelts; i++)
    {
      svn_boolean_t is_rolled_out;

      svn_wc__committable_external_info_t *xinfo =
        APR_ARRAY_IDX(orig_externals, i,
                      svn_wc__committable_external_info_t *);

      /* Discard dirs for svn_depth_files (s.a.). */
      if (depth == svn_depth_files
          && xinfo->kind == svn_node_dir)
        continue;

      svn_pool_clear(iterpool);

      /* Discard those externals that are not currently checked out. */
      SVN_ERR(is_external_rolled_out(&is_rolled_out, wc_ctx, xinfo,
                                     iterpool));
      if (! is_rolled_out)
        continue;

      if (*externals == NULL)
        *externals = apr_array_make(
                               result_pool, 0,
                               sizeof(svn_wc__committable_external_info_t *));

      APR_ARRAY_PUSH(*externals,
                     svn_wc__committable_external_info_t *) = xinfo;

      if (depth != svn_depth_infinity)
        continue;

      /* Are there any nested externals? */
      SVN_ERR(svn_wc__committable_externals_below(externals, wc_ctx,
                                                  xinfo->local_abspath,
                                                  svn_depth_infinity,
                                                  result_pool, iterpool));
    }

  return SVN_NO_ERROR;
}

svn_error_t *
svn_wc__externals_defined_below(apr_hash_t **externals,
                                svn_wc_context_t *wc_ctx,
                                const char *local_abspath,
                                apr_pool_t *result_pool,
                                apr_pool_t *scratch_pool)
{
  return svn_error_trace(
            svn_wc__db_externals_defined_below(externals,
                                               wc_ctx->db, local_abspath,
                                               result_pool, scratch_pool));
}

svn_error_t *
svn_wc__external_register(svn_wc_context_t *wc_ctx,
                          const char *defining_abspath,
                          const char *local_abspath,
                          svn_node_kind_t kind,
                          const char *repos_root_url,
                          const char *repos_uuid,
                          const char *repos_relpath,
                          svn_revnum_t operational_revision,
                          svn_revnum_t revision,
                          apr_pool_t *scratch_pool)
{
  SVN_ERR_ASSERT(kind == svn_node_dir);
  return svn_error_trace(
            svn_wc__db_external_add_dir(wc_ctx->db, local_abspath,
                                        defining_abspath,
                                        repos_root_url,
                                        repos_uuid,
                                        defining_abspath,
                                        repos_relpath,
                                        operational_revision,
                                        revision,
                                        NULL,
                                        scratch_pool));
}

svn_error_t *
svn_wc__external_remove(svn_wc_context_t *wc_ctx,
                        const char *wri_abspath,
                        const char *local_abspath,
                        svn_boolean_t declaration_only,
                        svn_cancel_func_t cancel_func,
                        void *cancel_baton,
                        apr_pool_t *scratch_pool)
{
  svn_wc__db_status_t status;
  svn_node_kind_t kind;

  SVN_ERR(svn_wc__db_external_read(&status, &kind, NULL, NULL, NULL, NULL,
                                   NULL, NULL,
                                   wc_ctx->db, local_abspath, wri_abspath,
                                   scratch_pool, scratch_pool));

  SVN_ERR(svn_wc__db_external_remove(wc_ctx->db, local_abspath, wri_abspath,
                                     NULL, scratch_pool));

  if (declaration_only)
    return SVN_NO_ERROR;

  if (kind == svn_node_dir)
    SVN_ERR(svn_wc_remove_from_revision_control2(wc_ctx, local_abspath,
                                                 TRUE, TRUE,
                                                 cancel_func, cancel_baton,
                                                 scratch_pool));
  else
    {
      SVN_ERR(svn_wc__db_base_remove(wc_ctx->db, local_abspath,
                                     FALSE /* keep_as_working */,
                                     TRUE /* queue_deletes */,
                                     FALSE /* remove_locks */,
                                     SVN_INVALID_REVNUM,
                                     NULL, NULL, scratch_pool));
      SVN_ERR(svn_wc__wq_run(wc_ctx->db, local_abspath,
                             cancel_func, cancel_baton,
                             scratch_pool));
    }

  return SVN_NO_ERROR;
}

svn_error_t *
svn_wc__externals_gather_definitions(apr_hash_t **externals,
                                     apr_hash_t **depths,
                                     svn_wc_context_t *wc_ctx,
                                     const char *local_abspath,
                                     svn_depth_t depth,
                                     apr_pool_t *result_pool,
                                     apr_pool_t *scratch_pool)
{
  if (depth == svn_depth_infinity
      || depth == svn_depth_unknown)
    {
      return svn_error_trace(
        svn_wc__db_externals_gather_definitions(externals, depths,
                                                wc_ctx->db, local_abspath,
                                                result_pool, scratch_pool));
    }
  else
    {
      const svn_string_t *value;
      svn_error_t *err;
      *externals = apr_hash_make(result_pool);

      local_abspath = apr_pstrdup(result_pool, local_abspath);

      err = svn_wc_prop_get2(&value, wc_ctx, local_abspath,
                             SVN_PROP_EXTERNALS, result_pool, scratch_pool);

      if (err)
        {
          if (err->apr_err != SVN_ERR_WC_PATH_NOT_FOUND)
            return svn_error_trace(err);

          svn_error_clear(err);
          value = NULL;
        }

      if (value)
        svn_hash_sets(*externals, local_abspath, value->data);

      if (value && depths)
        {
          svn_depth_t node_depth;
          *depths = apr_hash_make(result_pool);

          SVN_ERR(svn_wc__db_read_info(NULL, NULL, NULL, NULL, NULL, NULL,
                                       NULL, NULL, NULL, &node_depth, NULL,
                                       NULL, NULL, NULL, NULL, NULL, NULL,
                                       NULL, NULL, NULL, NULL, NULL, NULL,
                                       NULL, NULL, NULL, NULL,
                                       wc_ctx->db, local_abspath,
                                       scratch_pool, scratch_pool));

          svn_hash_sets(*depths, local_abspath, svn_depth_to_word(node_depth));
        }

      return SVN_NO_ERROR;
    }
}

svn_error_t *
svn_wc__close_db(const char *external_abspath,
                 svn_wc_context_t *wc_ctx,
                 apr_pool_t *scratch_pool)
{
  SVN_ERR(svn_wc__db_drop_root(wc_ctx->db, external_abspath,
                               scratch_pool));
  return SVN_NO_ERROR;
}

/* Return the scheme of @a uri in @a scheme allocated from @a pool.
   If @a uri does not appear to be a valid URI, then @a scheme will
   not be updated.  */
static svn_error_t *
uri_scheme(const char **scheme, const char *uri, apr_pool_t *pool)
{
  apr_size_t i;

  for (i = 0; uri[i] && uri[i] != ':'; ++i)
    if (uri[i] == '/')
      goto error;

  if (i > 0 && uri[i] == ':' && uri[i+1] == '/' && uri[i+2] == '/')
    {
      *scheme = apr_pstrmemdup(pool, uri, i);
      return SVN_NO_ERROR;
    }

error:
  return svn_error_createf(SVN_ERR_BAD_URL, 0,
                           _("URL '%s' does not begin with a scheme"),
                           uri);
}

svn_error_t *
svn_wc__resolve_relative_external_url(const char **resolved_url,
                                      const svn_wc_external_item2_t *item,
                                      const char *repos_root_url,
                                      const char *parent_dir_url,
                                      apr_pool_t *result_pool,
                                      apr_pool_t *scratch_pool)
{
  const char *url = item->url;
  apr_uri_t parent_dir_uri;
  apr_status_t status;

  *resolved_url = item->url;

  /* If the URL is already absolute, there is nothing to do. */
  if (svn_path_is_url(url))
    {
      /* "http://server/path" */
      *resolved_url = svn_uri_canonicalize(url, result_pool);
      return SVN_NO_ERROR;
    }

  if (url[0] == '/')
    {
      /* "/path", "//path", and "///path" */
      int num_leading_slashes = 1;
      if (url[1] == '/')
        {
          num_leading_slashes++;
          if (url[2] == '/')
            num_leading_slashes++;
        }

      /* "//schema-relative" and in some cases "///schema-relative".
         This last format is supported on file:// schema relative. */
      url = apr_pstrcat(scratch_pool,
                        apr_pstrndup(scratch_pool, url, num_leading_slashes),
                        svn_relpath_canonicalize(url + num_leading_slashes,
                                                 scratch_pool),
                        (char*)NULL);
    }
  else
    {
      /* "^/path" and "../path" */
      url = svn_relpath_canonicalize(url, scratch_pool);
    }

  /* Parse the parent directory URL into its parts. */
  status = apr_uri_parse(scratch_pool, parent_dir_url, &parent_dir_uri);
  if (status)
    return svn_error_createf(SVN_ERR_BAD_URL, 0,
                             _("Illegal parent directory URL '%s'"),
                             parent_dir_url);

  /* If the parent directory URL is at the server root, then the URL
     may have no / after the hostname so apr_uri_parse() will leave
     the URL's path as NULL. */
  if (! parent_dir_uri.path)
    parent_dir_uri.path = apr_pstrmemdup(scratch_pool, "/", 1);
  parent_dir_uri.query = NULL;
  parent_dir_uri.fragment = NULL;

  /* Handle URLs relative to the current directory or to the
     repository root.  The backpaths may only remove path elements,
     not the hostname.  This allows an external to refer to another
     repository in the same server relative to the location of this
     repository, say using SVNParentPath. */
  if ((0 == strncmp("../", url, 3)) ||
      (0 == strncmp("^/", url, 2)))
    {
      apr_array_header_t *base_components;
      apr_array_header_t *relative_components;
      int i;

      /* Decompose either the parent directory's URL path or the
         repository root's URL path into components.  */
      if (0 == strncmp("../", url, 3))
        {
          base_components = svn_path_decompose(parent_dir_uri.path,
                                               scratch_pool);
          relative_components = svn_path_decompose(url, scratch_pool);
        }
      else
        {
          apr_uri_t repos_root_uri;

          status = apr_uri_parse(scratch_pool, repos_root_url,
                                 &repos_root_uri);
          if (status)
            return svn_error_createf(SVN_ERR_BAD_URL, 0,
                                     _("Illegal repository root URL '%s'"),
                                     repos_root_url);

          /* If the repository root URL is at the server root, then
             the URL may have no / after the hostname so
             apr_uri_parse() will leave the URL's path as NULL. */
          if (! repos_root_uri.path)
            repos_root_uri.path = apr_pstrmemdup(scratch_pool, "/", 1);

          base_components = svn_path_decompose(repos_root_uri.path,
                                               scratch_pool);
          relative_components = svn_path_decompose(url + 2, scratch_pool);
        }

      for (i = 0; i < relative_components->nelts; ++i)
        {
          const char *component = APR_ARRAY_IDX(relative_components,
                                                i,
                                                const char *);
          if (0 == strcmp("..", component))
            {
              /* Constructing the final absolute URL together with
                 apr_uri_unparse() requires that the path be absolute,
                 so only pop a component if the component being popped
                 is not the component for the root directory. */
              if (base_components->nelts > 1)
                apr_array_pop(base_components);
            }
          else
            APR_ARRAY_PUSH(base_components, const char *) = component;
        }

      parent_dir_uri.path = (char *)svn_path_compose(base_components,
                                                     scratch_pool);
      *resolved_url = svn_uri_canonicalize(apr_uri_unparse(scratch_pool,
                                                           &parent_dir_uri, 0),
                                       result_pool);
      return SVN_NO_ERROR;
    }

  /* The remaining URLs are relative to either the scheme or server root
     and can only refer to locations inside that scope, so backpaths are
     not allowed. */
  if (svn_path_is_backpath_present(url))
    return svn_error_createf(SVN_ERR_BAD_URL, 0,
                             _("The external relative URL '%s' cannot have "
                               "backpaths, i.e. '..'"),
                             item->url);

  /* Relative to the scheme: Build a new URL from the parts we know. */
  if (0 == strncmp("//", url, 2))
    {
      const char *scheme;

      SVN_ERR(uri_scheme(&scheme, repos_root_url, scratch_pool));
      *resolved_url = svn_uri_canonicalize(apr_pstrcat(scratch_pool, scheme,
                                                       ":", url, (char *)NULL),
                                           result_pool);
      return SVN_NO_ERROR;
    }

  /* Relative to the server root: Just replace the path portion of the
     parent's URL. */
  if (url[0] == '/')
    {
      parent_dir_uri.path = (char *)url;
      *resolved_url = svn_uri_canonicalize(apr_uri_unparse(scratch_pool,
                                                           &parent_dir_uri, 0),
                                           result_pool);
      return SVN_NO_ERROR;
    }

  return svn_error_createf(SVN_ERR_BAD_URL, 0,
                           _("Unrecognized format for the relative external "
                             "URL '%s'"),
                           item->url);
}
