restack appears to enter infinite loop when it encounters a merge conflict

[jacobsimpson-addepar]

When I amend to an older commit in the stack that results in a merge conflict, I get repeated errors indicating a rebase is in progress:

branchless: git rebase b5ed1de43634dc9e64ab9a0e0d1555f6a2c41297 06e73bfc36ab4f7b83a6abbda1e24c55aa3435c5 --onto 69feacd33c46f8c4bdf053d7f778e2077bdfee56
Auto-merging README.md
CONFLICT (content): Merge conflict in README.md
Rebasing (1/1)^Mbranchless: processing 1 update to a branch/ref
branchless: processing 1 update to a branch/ref
error: could not apply 06e73bf... Make line 2 extra verbose
Resolve all conflicts manually, mark them as resolved with
"git add/rm <conflicted_files>", then run "git rebase --continue".
You can instead skip this commit: run "git rebase --skip".
To abort and get back to the state before "git rebase", run "git rebase --abort".
branchless: processing 1 update to a branch/ref
Recorded preimage for 'README.md'
branchless: processing 1 update to a branch/ref
Could not apply 06e73bf... Make line 2 extra verbose
branchless: resolve rebase, then run 'git restack' again
branchless: git rebase b5ed1de43634dc9e64ab9a0e0d1555f6a2c41297 06e73bfc36ab4f7b83a6abbda1e24c55aa3435c5 --onto 69feacd33c46f8c4bdf053d7f778e2077bdfee56
fatal: It seems that there is already a rebase-merge directory, and
I wonder if you are in the middle of another rebase.  If that is the
case, please try
        git rebase (--continue | --abort | --skip)
If that is not the case, please
        rm -fr ".git/rebase-merge"
and run me again.  I am stopping in case you still have something
valuable there.

branchless: resolve rebase, then run 'git restack' again
branchless: git rebase b5ed1de43634dc9e64ab9a0e0d1555f6a2c41297 06e73bfc36ab4f7b83a6abbda1e24c55aa3435c5 --onto 69feacd33c46f8c4bdf053d7f778e2077bdfee56
fatal: It seems that there is already a rebase-merge directory, and
I wonder if you are in the middle of another rebase.  If that is the
case, please try
        git rebase (--continue | --abort | --skip)
If that is not the case, please
        rm -fr ".git/rebase-merge"
and run me again.  I am stopping in case you still have something
valuable there.

The last bit repeats endlessly.

Repro:

mkdir -p origin-repo
cd origin-repo
git init .
printf "one\ntwo\nthree\n" > README.md
git add .
git commit -am "Initial commit."
cd ..
git clone origin-repo/.git cloned-repo
cd cloned-repo
git branchless init
git checkout -b feature-1
cp README.md tmp && sed '2s/^/lin /' < tmp > README.md && rm tmp
git commit -am "Update line 2."
git checkout -b feature-2
cp README.md tmp && sed '2s/^/this is /' < tmp > README.md && rm tmp
git commit -am "Make line 2 extra verbose"
git prev
cp README.md tmp && sed '2s/^lin /line /' < tmp > README.md && rm tmp
git amend -a
git restack

If you run into this in the wild:

1. Break the loop w/ Ctrl-C
2. Resolve the conflict by editing the conflicted file (README.md in the repro).
3. git add README.md
4. git rebase --continue
5. git restack

[arxanas]

Thanks for the detailed report and repro steps. I wasn't able to to reproduce this, with this slightly modified script (git amend doesn't exist in stock Git):

mkdir -p origin-repo
cd origin-repo
git init .
printf "one\ntwo\nthree\n" > README.md
git add .
git commit -am "Initial commit."
cd ..
git clone origin-repo/.git cloned-repo
cd cloned-repo
git branchless init
git checkout -b feature-1
cp README.md tmp && sed '2s/^/lin /' < tmp > README.md && rm tmp
git commit -am "Update line 2."
git checkout -b feature-2
cp README.md tmp && sed '2s/^/this is /' < tmp > README.md && rm tmp
git commit -am "Make line 2 extra verbose"
git prev
cp README.md tmp && sed '2s/^lin /line /' < tmp > README.md && rm tmp
git commit -a --amend
git restack

Most likely this was fixed in 15fe104, released in https://github.com/arxanas/git-branchless/releases/tag/v0.3.2. I would ask what version of git-branchless you're using, but it might be hard to say, given that git-branchless doesn't correctly report its version number (9d4f4f1)... Reopen if the issue persists after upgrading to v0.3.2 or later.

git restack is implemented in kind of a hacky way for now. In the long run, I'd like to use the git move machinery to form a rebase plan and execute it all in one go, rather than iterating until we reach a fixed point. This should make it much harder to hit an infinite loop bug because we won't be doing any looping.

[jacobsimpson-addepar]

Oops, I forgot that amend is an alias. You guessed it correctly in any case.

Issue is gone after upgrading.