dump/load mergeinfo-mod difference with --deltas

When a revision has a property change that is not an svn:mergeinfo change to a node that already has svn:mergeinfo then a dump/load of that revision produces different representations in the new repository depending on whether --deltas is used when dumping.

The original repository:

svnadmin create repo
svnmucc -mm -U file://`pwd`/repo mkdir A
svnmucc -mm -U file://`pwd`/repo propset svn:mergeinfo /B:1 A
svnmucc -mm -U file://`pwd`/repo propset p2 v2 A

Dump and load with/without --deltas

svnadmin dump repo | svnadmin load repo2
svnadmin dump --deltas repo | svnadmin load repo3

Note the difference in the r3 revision files:

$ grep -a modify-dir repo[23]/db/revs/0/3

repo2/db/revs/0/3:0-1.0.t2-2 modify-dir false true true /A
repo3/db/revs/0/3:0-1.0.t2-2 modify-dir false true false /A

Using --deltas has produced the correct value, the revision has no mergeinfo change.

The field that differs is mergeinfo-mod, introduced in 1.9. The problem doesn't occur in earlier versions.