[PATCH 0/6] Fix various rename corner cases

["Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>]

At GitHub, we've got a real-world repository that has been triggering
failures of the form:

git: merge-ort.c:3007: process_renames: Assertion `newinfo && !newinfo->merged.clean' failed.


Digging in, this particular corner case requires multiple things to trigger:
(1) a rename/delete of one file, and (2) a directory rename modifying an
unrelated rename such that this unrelated rename's target becomes the source
of the rename/delete from (1).

Unfortunately, looking around, it's not the only bug in the area. Plus, some
of our testcases in tangential situations were not checked closely enough or
were weird or buggy in various ways. Adding to the challenge was the fact
that the relevant renames optimization was sometimes triggering making
renames look like delete-and-add, and overlooking this meant I sometimes
wasn't triggering what I thought I was triggering.

The combination of challenges sometimes made me think my fixes were breaking
things when sometimes I was just unaware of other bugs. I went in circles a
few times and took a rather non-linear path to finding and fixing these
issues. While I think I've turned it into a nice linear progression of
patches, I might be a bit too deep in the mud and it might not be as linear
or clear as I think. Let me know and I'll try to clarify anything needed.

Elijah Newren (6):
  merge-ort: update comments to modern testfile location
  merge-ort: drop unnecessary temporary in check_for_directory_rename()
  t6423: document two bugs with rename-to-self testcases
  t6423: fix missed staging of file in testcases 12i,12j,12k
  merge-ort: fix incorrect file handling
  merge-ort: fix directory rename on top of source of other
    rename/delete

 merge-ort.c                         |  41 ++-
 t/t6423-merge-rename-directories.sh | 520 +++++++++++++++++++++++++++-
 2 files changed, 534 insertions(+), 27 deletions(-)


base-commit: 16bd9f20a403117f2e0d9bcda6c6e621d3763e77
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1943%2Fnewren%2Ffix-rename-corner-cases-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1943/newren/fix-rename-corner-cases-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/1943
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