Philippe Blain found and reported a couple issues with the output of
--remerge-diff[1]. After digging in, I think one of them actually counts as
two separate issues, so here's a series with three patches to fix these
issues. Each includes testcases to keep us from regressing.

Changes since v1:

 * Added a new diff_filepair_is_phoney() function to make the code more
   self-documenting, as suggested by Junio.
 * Note: Patch 2, as called out in its commit message, disables
   TEST_PASSES_SANITIZE_LEAK for t4069. This is not because I introduce any
   memory leaks, but because I add new testcases invoking additional parts
   of the code (pickaxe stuff) which already had pre-existing leaks. This is
   not a change since v1, but this somehow accidentally got munged out of
   Junio's application of my v1.

Note: The issue fixed by the third commit for --remerge-diff is also an
issue exhibited by 'git log --cc $FILTER_RULES $COMMIT' (or by -c instead of
--cc). However, as far as I can tell the causes are different and come from
separate codepaths; this series focuses on --remerge-diff and hence makes no
attempt to fix independent (even if similar) --cc or -c issues.

[1]
https://lore.kernel.org/git/43cf2a1d-058a-fd79-befe-7d9bc62581ed@gmail.com/

Elijah Newren (3):
  diff: have submodule_format logic avoid additional diff headers
  diff: fix filtering of additional headers under --remerge-diff
  diff: fix filtering of merge commits under --remerge-diff

 diff.c                  | 17 ++++++++++++++---
 t/t4069-remerge-diff.sh | 30 +++++++++++++++++++++++++++++-
 2 files changed, 43 insertions(+), 4 deletions(-)

base-commit: 6c8e4ee870332d11e4bba84901654b355a9ff016

Submitted-As: https://lore.kernel.org/git/pull.1342.v2.git.1662016087.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1342.git.1661926908.gitgitgadget@gmail.com