[SVN-2897] Reflective merges are faulty

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: trunk
• Fix Version/s: 1.8-consider
• Component/s: libsvn_client
• Labels: merge-tracking
• Assignee: Unassigned
• Reporter: Subversion Importer
• Created: 30/Aug/07 12:12
• Updated: 27/Oct/18 16:27
• Resolved: 11/Apr/13 21:15

Description

While studying merge.c to fix issue 2821, I came across the following snippet of
code which suggested a bug to me.

<snip from calculate_requested_merges>
  if (added_mergeinfo)
    {
      const char *src_rel_path;
      SVN_ERR(svn_client__path_relative_to_root(&src_rel_path, entry->url,
                                                entry->repos, ra_session,
                                                adm_access, pool));
      src_rangelist_for_tgt = apr_hash_get(added_mergeinfo, src_rel_path,
                                           APR_HASH_KEY_STRING);
    }
</snip>

The above logic is wrong, take the following usecase,
1)We branched /trunk as /fb at r51.(Now /fb has a mergeinfo of /trunk: 1-50)
2)We did changes to /fb at r52 and r53
3)Synched up the changes from /trunk to /fb via a merge and committed the merge
at r60(Now /fb has a mergeinfo of /trunk: 1-59)
4)Did some changes to /fb at r61, r62
5)Merge -r51:62 $URL_to/fb to $WC_of_trunk
Now our above reflective logic code removes '51:59' from '51:62' and hence just
merges '60:62' and hence does a bogus possible conflict and never merges the
commits '/fb' prior to synch up from the '/trunk' to '/fb'.

Attaching simple shell script to prove the problem.

Original issue reported by kameshj