Bug#921124: elpa-git-commit: bad interaction with worktree/branch renaming

[Robbie Harwood <rharwood@club.cc.cmu.edu>]

Package: elpa-git-commit
Version: 2.90.1-1
Followup-For: Bug #921124

Thanks for your patience while I investigated a bit further.

It appears that this is related to worktrees and branch migration.  I can
reproduce like so:

    # set up repo
    git init testrepo
    cd testrepo

    # make HEAD valid so worktrees work
    echo test > testf
    git add testf
    git commit -m test

    # muck about with worktrees
    git worktree add ugly-1
    mv ugly-1 ugly-2
    cd ugly-2
    git branch -m ugly-2

    # try to commit
    echo test2 > testf
    git commit -a

Assuming that's set up to spawn emacs with elpa-magit/elpa-git-commit, you
should see the failure at that point (warning that it renders my terminal
near-useless).  The content of *Messages* is:

    Diffing changes to be committed (C-g to abort diffing)
    Type C-c C-c to finish, or C-c C-k to cancel
    error in process sentinel: user-error: Don’t kill this buffer.  Instead cancel using C-c C-k
    error in process sentinel: Don’t kill this buffer.  Instead cancel using C-c C-k

Both (cli-only git) and (cli-git with emacs as editor but no magit) to have no
problem committing here.

Deleting and recreating the worktree using the new branchname seems to resolve
the problem.

Thanks,
--Robbie

-- System Information:
Debian Release: buster/sid
  APT prefers testing-debug
  APT policy: (700, 'testing-debug'), (700, 'testing'), (500, 'unstable-debug'), (500, 'unstable'), (300, 'experimental-debug'), (300, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-2-rt-amd64 (SMP w/4 CPU cores; PREEMPT)
Locale: LANG=es_US.UTF-8, LC_CTYPE=es_US.UTF-8 (charmap=UTF-8), LANGUAGE=es_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages elpa-git-commit depends on:
ii  elpa-dash         2.14.1+dfsg-1
ii  elpa-with-editor  2.8.1-1
ii  emacsen-common    3.0.4

elpa-git-commit recommends no packages.

elpa-git-commit suggests no packages.

-- no debconf information