"Repository has no commit" error in case of worktree + packed-refs

[vikukush]

After git decided to pack my repo with several worktrees and a bunch of local branches, my builds started failing with following error:

D:\Corextroot\microsoft.build.tasks.git\8.0.0\build\Microsoft.Build.Tasks.Git.targets(25,5): Repository has no commit. [D:\Pl3\Test\UnitTests\Common\Tools.UnitTests.Common\Tools.UT.Common.csproj]

• D:\Pl3 is a worktree of D:\Platform.
• D:\Platform\.git\worktrees\Pl3\refs is empty.
• D:\Platform\.git\refs\heads doesn't have a ref of a branch that's checked out in D:\Pl3 either
• The only reference to the commit ID of a branch specified in D:\Platform\.git\worktrees\Pl3\HEAD is in D:\Platform\.git\packed-refs

Sourcelink task is unable to handle this situation.

I have worked to add a unit test that covers my scenario: #1289

[vikukush]

The issue went away after I created the very next commit, which created D:\Platform.git\refs\heads\user\vikukush\mstestv3 file, so the commit ID was no longer inside packed-refs.
So the bug can be easily worked around, but this of course still needs to be fixed.

[bradwilson]

I just started using git worktree and ran into this.

Any progress here, or even an acknowledgment from the team that it's an issue to be fixed?

[tmat]

Will take a look.

[tmat]

The path D:\Corextroot\microsoft.build.tasks.git\8.0.0 indicates that you're using .NET SDK 8.0. Does the issue reproduce with .NET SDK 10?

[jjonescz]

I'm hitting this too. I'm using Microsoft.Build.Tasks.Git from .NET SDK 10.0.105. It seems this happens when the HEAD ref is packed, i.e., there is no file under refs/heads/ for it in .git folder, it's only in .git/packed-refs. Can be worked around by creating a new commit (since that one won't be packed yet).

[tmat]

@jjonescz Do you have repro steps how do you get the repo to that state?

[jjonescz]

I can try to create a small repro if you want. But based on my analysis, if you use git pack-refs to make the current HEAD a packed ref, that should be it. It seems there is even a PR with a unit test for this (which seems correct at a high level to me): https://github.com/dotnet/sourcelink/pull/1289/changes

[tmat]

I tried to repro with out of our repos, using git pack-refs --all -- this removed refs/heads files but source link was still working (getting the commit sha from the packed refs).

[tmat]

Never mind. I think I see the issue. The docs https://git-scm.com/docs/git-pack-refs say the packed-refs file is in $GIT_DIR, but it's actually in $GIT_COMMON_DIR. This is mentioned in https://git-scm.com/docs/gitrepository-layout#Documentation/gitrepository-layout.txt-packed-refs.