Why doesn't git move do anything in worktrees?

[miquella]

Hello wonderful friends!

I've been quite confused by git move for a long time and believe I realized why today: worktrees!

Background

I tend to have a lot of incomplete streams of work that I switch between often, so I have several worktrees open at any given time (although git-branchless has helped to reduce this quite a bit, I haven't completely kicked the habit just yet 😜). To make matters worse, I tend to not use branches either.

While working in one of these branchless worktrees, I often come across an unrelated issue. So I fix the issue and commit it separate from the rest of my work. Once I reach a stopping point, I cherry-pick those changes onto the main branch and rebase them out of my commit history.

Confusion

Once I picked up git-branchless, I realized that I could simplify (or so I thought…) this workflow by using git move!

The thing that's always confused me is that it never seemed to work. I would git move -x <COMMIT> -d <MAIN> and … nothing would change. Or worse, sometimes the commit would just be gone! Thankfully, when it was missing, some combination of git undo and/or scouring the output would allow me to recover the missing commit.

Today while trying to figure out what was going on, I realized this only fails in worktrees 😮 If I switched to my standard clone, everything works fine!

So my question is: am I doing something wrong? Perhaps I'm just expecting the wrong thing?

Demo

To demonstrate the issue, I setup a new repo:

$ mkdir branchless-demo
$ cd branchless-demo
$ git init
$ git branchless init --main-branch master

$ printf 'A\nB\nD\n' > README.md
$ git add README.md
$ git commit -m 'README'
[master (root-commit) e7d9765] README
 1 file changed, 3 insertions(+)
 create mode 100644 README.md

Switched to a worktree:

$ git worktree add --detach ../branchless-demo-2
Preparing worktree (detached HEAD e7d9765)
branchless: processing 1 update: ref HEAD
branchless: processing 1 update: ref HEAD
HEAD is now at e7d9765 Something else
branchless: processing checkout
$ cd ../branchless-demo-2

And did some "work":

$ touch something.txt
$ git add something.txt
$ git commit -m 'Something'
branchless: processing 1 update: ref HEAD
branchless: processed commit: 12e5739 Something
[detached HEAD 12e5739] Something
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 something.txt

$ printf 'A\nB\nC\nD\n' > README.md
$ git add README.md
$ git commit -m 'Update README'
branchless: processing 1 update: ref HEAD
branchless: processed commit: 0adb2e7 Update README
[detached HEAD 0adb2e7] Update README
 1 file changed, 1 insertion(+)

$ touch something_else.txt
$ git add something_else.txt
$ git commit -m 'Something else'
branchless: processing 1 update: ref HEAD
branchless: processed commit: bf05214 Something else
[detached HEAD bf05214] Something else
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 something_else.txt

$ git sl
◇ e7d9765 1m (master) README
┃
◯ 12e5739 32s Something
┃
◯ 0adb2e7 12s Update README
┃
● bf05214 2s Something else

Then attempt to move something:

$ git move -x 0adb2e7 -d e7d9765
Attempting rebase in-memory...
[1/2] Committed as: d0dc1ac Something else
[2/2] Committed as: 58762a1 Update README
branchless: creating working copy snapshot
branchless: running command: git checkout d0dc1ace840fd1715329e8a15a094ddc2558ce2c
Previous HEAD position was bf05214 Something else
branchless: processing 1 update: ref HEAD
HEAD is now at d0dc1ac Something else
branchless: processing checkout
◇ e7d9765 41m (master) README
┃
◯ 12e5739 40m Something
┃
● d0dc1ac 0s Something else
In-memory rebase succeeded.

But now the "Update README" commit is gone from the smartlog! I've learned that if I carefully read the output, I can unhide the commit and then the smartlog appears as I would expect:

$ git unhide 58762a1
Unhid commit: 58762a1 Update README
To hide this 1 commit, run: git undo
$ git sl
◇ e7d9765 44m (master) README
┣━┓
┃ ◯ 12e5739 43m Something
┃ ┃
┃ ● d0dc1ac 2m Something else
┃
◯ 58762a1 2m Update README

[miquella]

It does make me wonder if this is somehow related to #215?

[arxanas]

I haven't taken a look, but you might need to run git branchless init in the worktrees to install hooks.

[miquella]

Good thought!

Running git branchless init in the worktree doesn't appear to have changed anything:

$ cd branchless-demo-2
$ git branchless init
Created config file at /Users/miquella/src/branchless-demo/.git/branchless/config
Auto-detected your main branch as: master
If this is incorrect, run: git branchless init --main-branch <branch>
Installing hook: post-commit
Installing hook: post-merge
Installing hook: post-rewrite
Installing hook: post-checkout
Installing hook: pre-auto-gc
Installing hook: reference-transaction
Successfully installed git-branchless.
To uninstall, run: git branchless init --uninstall

$ git sl
◇ e7d9765 6d (master) README
┃
◯ 12e5739 6d Something
┃
◯ 0adb2e7 6d Update README
┃
● bf05214 6d Something else

$ git move -x 0adb2e7 -d e7d9765
Attempting rebase in-memory...
[1/2] Committed as: c04d12b Something else
[2/2] Committed as: 0ef1c57 Update README
branchless: creating working copy snapshot
branchless: running command: git checkout c04d12b33f99e9c876826d5d6844946803357a78
Previous HEAD position was bf05214 Something else
branchless: processing 1 update: ref HEAD
HEAD is now at c04d12b Something else
branchless: processing checkout
◇ e7d9765 6d (master) README
┃
◯ 12e5739 6d Something
┃
● c04d12b 1s Something else
In-memory rebase succeeded.

The resulting commit (0ef1c57) still needed to be passed into git unhide for it to show up in the smartlog:

$ git unhide 0ef1c57
Unhid commit: 0ef1c57 Update README
To hide this 1 commit, run: git undo

$ git sl
◇ e7d9765 6d (master) README
┣━┓
┃ ◯ 12e5739 6d Something
┃ ┃
┃ ● c04d12b 2m Something else
┃
◯ 0ef1c57 2m Update README

Correlating this with the repository layout docs seems to confirm that worktrees do share hooks with the original repo (although I'm not sure if git-branchless is doing much outside of the hooks).

[arxanas]

A colleague of mine reported problems with relative worktrees. Can you try with an absolute path to the worktree and see if that resolves the issue?

[miquella]

Oh, great idea!

Unfortunately, it looks like it's already an absolute path:

$ cat .git
gitdir: /Users/miquella/src/branchless-demo/.git/worktrees/branchless-demo-2

[arxanas]

In my case, git commit indicates that it is invoking git-branchless hooks. That is, instead of

$ git commit -m 'README'
[master (root-commit) e7d9765] README
 1 file changed, 3 insertions(+)
 create mode 100644 README.md

I get

$ git commit -m 'README'
branchless: processing 2 updates: branch master, ref HEAD
branchless: processed commit: 94fa741 README
[master (root-commit) 94fa741] README
1 file changed, 3 insertions(+)
create mode 100644 README.md

Although later I see that your reference-transaction and post-commit hooks seem to have triggered properly.

After following along with the rest of the steps, it didn't reproduce, and the git move invocation immediately showed the new commits:

$ git sl
◇ 94fa741 3m (master) README
┃
◯ f4e2e91 2m Something
┃
◯ e31bf9c 1m Update README
┃
● 4856148 1m Something else
$ git move -s e31bf9c -d 94fa741
Attempting rebase in-memory...
[1/2] Committed as: 81816d2 Update README
[2/2] Committed as: 7118d31 Something else
branchless: creating working copy snapshot
branchless: running command: git checkout 7118d31fc9dbcc989d543b2a2426f0e1cce80bbc
Previous HEAD position was 4856148 Something else
branchless: processing 1 update: ref HEAD
HEAD is now at 7118d31 Something else
branchless: processing checkout
◇ 94fa741 3m (master) README
┣━┓
┃ ◯ f4e2e91 2m Something
┃ ┃
┃ ◯ e31bf9c 1m Update README
┃ ┃
┃ ◯ 4856148 1m Something else
┃
◯ 81816d2 0s Update README
┃
● 7118d31 0s Something else
In-memory rebase succeeded.

Perhaps your hooks are installed incorrectly (if you use husky, it may overwrite them aggressively), or your version of Git is too old. Could you reproduce the issue and upload the output of git-branchless bug-report? Also, after reproducing it in a worktree, run the same bug-report command in the main worktree as well and upload both, as I see now that they may report different hooks as having been installed. The bug-report subcommand will sanitize the commit graph and branch names, so you can try it on your real repo if you're comfortable with that.

[arxanas]

I was wrong; I think I never noticed the problems with worktrees in my previous usage. I opened #1095 to address this.

But now the "Update README" commit is gone from the smartlog!

The problem is that it was never reachable from the worktree event log to begin wit — iIt happened to be visible in the smartlog only because it was reachable by HEAD. Once we rebase and switch commits, we are no longer at the old HEAD and it's no longer visible in the worktree.