"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.