bdiff: normalize the diff (
issue1295)
When the common part of a diff can be moved forward, move it forward.
Otherwise we don't get deterministic results (it would depends on the way we
split for the recursion).
That way we get identical hunks when doing the same change, it helps to solve
issue1295 (inconsistent diffs on different side during a merge).
% before commit
% store can be written by the group, other files cannot
% store is setgid
00700 ./.hg/
00600 ./.hg/00changelog.i
00600 ./.hg/requires
00770 ./.hg/store/
% after commit
% working dir files can only be written by the owner
% files created in .hg can be written by the group
% (in particular, store/**, dirstate, branch cache file, undo files)
% new directories are setgid
00700 ./.hg/
00600 ./.hg/00changelog.i
00660 ./.hg/dirstate
00600 ./.hg/requires
00770 ./.hg/store/
00660 ./.hg/store/00changelog.i
00660 ./.hg/store/00manifest.i
00770 ./.hg/store/data/
00770 ./.hg/store/data/dir/
00660 ./.hg/store/data/dir/bar.i
00660 ./.hg/store/data/foo.i
00660 ./.hg/store/undo
00660 ./.hg/undo.branch
00660 ./.hg/undo.dirstate
00700 ./dir/
00600 ./dir/bar
00600 ./foo
% before push
% group can write everything
00770 ../push/.hg/
00660 ../push/.hg/00changelog.i
00660 ../push/.hg/requires
00770 ../push/.hg/store/
% after push
% group can still write everything
00770 ../push/.hg/
00660 ../push/.hg/00changelog.i
00660 ../push/.hg/branch.cache
00660 ../push/.hg/requires
00770 ../push/.hg/store/
00660 ../push/.hg/store/00changelog.i
00660 ../push/.hg/store/00manifest.i
00770 ../push/.hg/store/data/
00770 ../push/.hg/store/data/dir/
00660 ../push/.hg/store/data/dir/bar.i
00660 ../push/.hg/store/data/foo.i
00660 ../push/.hg/store/undo
00660 ../push/.hg/undo.branch
00660 ../push/.hg/undo.dirstate