A patch that changes the filetype (e.g. regular file to symlink) of a path
must be split into a deletion event followed by a creation event, which
means that we need to have two independent metainfo lines for each.
However, the code reused the single set of metainfo lines.
As the blob object names recorded on the index lines are usually not used
nor validated on the receiving end, this is not an issue with normal use
of the resulting patch. However, when accepting a binary patch to delete
a blob, git-apply verified that the postimage blob object name on the
index line is 0{40}, hence a patch that deletes a regular file blob that
records binary contents to create a blob with different filetype (e.g. a
symbolic link) failed to apply. "git am -3" also uses the blob object
names recorded on the index line, so it would also misbehave when
synthesizing a preimage tree.
This moves the code to generate metainfo lines around, so that two
independent sets of metainfo lines are used for the split halves.
Additional tests by Jeff King.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
I've found that git apply is incapable of handling patches
involving object type changes to the same path.
Of course git itself is perfectly capable of making commits that
generate these changes, as it only tracks trees states. It's
just that the diffs between them are less useful if they can't
be applied.
Some of these are rare, but I've hit one of them (file becoming
a symlink) recently in real-world usage, and was inspired to
find more potential breakages :)
I'm not sure when I'll have time to fix these myself and I'm not
very familiar with the apply code. So if someone could get
some or all of these cases working, they would be my hero :)
Some of these are what I would refer to as corner-cases from
hell. Most (if not all) other systems fail some of these. In
fact, they aren't even capable of representing most of these
changes in their histories; much less being able to handle
patches to that effect.
Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>
