Lockfile issues

[dabrahams]

This happened to me today:

  1 git … imerge merge origin/interpreter
Attempting automerge of 8-61...failure.
Attempting automerge of 1-1...Traceback (most recent call last):
  File "/opt/homebrew/bin/git-imerge", line 8, in <module>
    sys.exit(climain())
             ~~~~~~~^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 4199, in climain
    main(sys.argv[1:])
    ~~~~^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 4170, in main
    cmd_merge(parser, options)
    ~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 3364, in cmd_merge
    merge_state.auto_complete_frontier()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 2659, in auto_complete_frontier
    frontier.auto_expand()
    ~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 1978, in auto_expand
    if block.auto_expand_frontier():
       ~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 2285, in auto_expand_frontier
    return self.auto_outline_frontier()
           ~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 2249, in auto_outline_frontier
    merge_frontier = MergeFrontier.compute_by_bisection(self)
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 1627, in compute_by_bisection
    return MergeFrontier(block, list(find_frontier_blocks(block)))
                                ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 1357, in find_frontier_blocks
    if not block.is_mergeable(1, 1):
           ~~~~~~~~~~~~~~~~~~^^^^^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 2130, in is_mergeable
    self.git.automerge(self[i1, 0].sha1, self[0, i2].sha1)
    ~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 655, in automerge
    call_silently(['git', 'checkout', '-f', commit1])
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/homebrew/Cellar/git-imerge/1.2.0_1/libexec/lib/python3.13/site-packages/gitimerge.py", line 230, in call_silently
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['git', 'checkout', '-f', '34a8975a4b899858936aa164c66133c695bf03e1']' returned non-zero exit status 128.

Reproduction should be possible:

1. Check out the git-imerge-traceback tag of https://github.com/hylo-lang/hylo as a local interpreter branch
2. git-imerge merge origin/interpreter.

[dabrahams]

Bump. It's happening again on a new repository.

[dabrahams]

Solved: This was happening due to Xcode running git in the background, unbidden, while this process was ongoing; there was a lockfile. It's their bug IMO but perhaps consider retrying git commands after a short delay when they fail for that reason.

[dabrahams]

Actually, git-imerge should probably create the lock file before starting and only remove it when exiting. Otherwise it can be left in a partially completed state from which it can't recover. Oh, that won't work unless there's a way to tell git to bypass acquiring the lockfile itself.