This adds #3ALT rule (and #2ALT rule for symmetry) to the
read-tree 3-way merge logic that collapses paths that are added
only in one branch and not in the other internally.
This makes --emu23 to succeed in the last remaining case where
the pure 2-way merge succeeded and earlier one failed. Running
diff between t1001 and t1005 test scripts shows that the only
difference between the two is that --emu23 can leave the states
into separate stages so that the user can use usual 3-way merge
resolution techniques to carry forward the local changes when
pure 2-way merge would have refused to run.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This fixes too strong index requirement 3-way merge enforces in
one case: the same file is added in both branches.
In this case, the original code insisted that if the index file
has that path, it must match our branch and be up-to-date.
However in this particular case, it only has to match it, and
can be dirty. We just need to make sure that we keep the
work-tree copy instead of checking out the merge result.
The resolution of such a path, however, cannot be left to
outside script, because we will not keep the original stage0
entries for unmerged paths when read-tree finishes, and at that
point, the knowledge of "if we resolve it to match the new file
added in both branches, the merge succeeds and the work tree
would not lose information, but we should _not_ update the work
tree from the resulting index file" is lost. For this reason,
the now code needs to resolve this case (#5ALT) internally.
This affects some existing tests in the test suite, but all in
positive ways. In t1000 (3-way test), this #5ALT case now gets
one stage0 entry, instead of an identical stage2 and stage3
entry pair, for such a path, and one test that checked for merge
failure (because the test assumed the "stricter-than-necessary"
behaviour) does not have to fail anymore. In t1005 (emu23
test), two tests that involves a case where the work tree
already had a change introduced in the upstream (aka "merged
head"), the merge succeeds instead of failing.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This new flag causes two-way fast forward to internally use the
three-way merge mechanism. This behaviour is intended to offer
a better fast forward semantics when used in a dirty work tree.
The new test t1005 is parallel to the existing t1001 "pure
2-way" tests, but some parts that are commented out would fail.
These failures are due to three-way merge enforcing too strict
index requirements for cases that could succeed. This problem
will be addressed by later patches.
Without even changing three-way mechanism, the --emu23 two-way
fast forward already gives the user an easier-to-handle merge
result when a file that "merged head" updates has local
modifications. This is demonstrated as "case 16" test in t1005.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
