[WIP PATCH 0/6] Merging with D/F conflicts

[Junio C Hamano <gitster@pobox.com>]

I have been working on this on-and-off and it still is not finished, but I
thought it would be a good place to stop, especially since this will not
be part of the upcoming 1.6.5 anyway.

The first three patches are preparatory clean-ups.

The fourth patch roughly corresponds to Linus's 880386c (Prepare
'traverse_trees()' for D/F conflict lookahead, 2009-09-06), but it does
implement multi-entry lookahead.  It reveals why lookahead on the tree
side alone is not sufficient by breaking a few tests.

The fifth one starts to compensate for the change in the tree side by
preparing the side that walks the index for a similar lookahead mechanism,
but it does not actually implement the lookahead yet.

The last one is a debugging patch.

This change has to break the output order (but not content) of the
diff-index somewhat.  If you had this:

    Index    Tree
    b        b-2/c
    b-2      b/d

the expected output order from diff-index is b, b-2, b-2/c, then b/d.  But
if you walk the tree and the index in parallel, we would end up showing b,
b/d, b-2 and then b-2/c.  A sad part of the story is that diff-index
always emits D/F conflicted entries as two independent records, so it is
rather a bad match to the unpack_trees() framework to begin with.

The patches are designed to apply on 79b4fde (Merge branch 'maint',
2009-09-03).

Junio C Hamano (6):
  diff-lib.c: fix misleading comments on oneway_diff()
  unpack-trees: typofix
  unpack_callback(): use unpack_failed() consistently
  traverse_trees(): handle D/F conflict case sanely
  unpack-trees.c: prepare for looking ahead in the index
  read-tree --debug-unpack

 builtin-read-tree.c |   36 +++++++
 cache.h             |    2 +
 diff-lib.c          |   20 +----
 tree-walk.c         |  277 +++++++++++++++++++++++++++++++++++++++++++--------
 unpack-trees.c      |  275 ++++++++++++++++++++++++++++++++++++++------------
 unpack-trees.h      |    3 +-
 6 files changed, 484 insertions(+), 129 deletions(-)