Sourcelink unable to find .git directory in linked working tree

[jkoritzinsky]

When using git worktree add to create a second working tree, the SourceLink package is unable to locate the .git folder for the repository when in the linked working tree.

The .git folder is hard-linked to the location in the primary working tree's .git folder where the data is stored, which SourceLink (along with a wide variety of Windows programs it seems) doesn't understand how to traverse into.

[tmat]

SourceLink didn't trim the trailing whitespace of commondir file. #406 fixes that.
To work around delete the trailing \n in repo\.git\worktrees\{worktree}\commondir files for each worktree.

[dagood]

Workaround doesn't work for me. Removing the trailing newline before Build.cmd in my repro steps at dotnet/arcade#3864 still shows errors:

...
C:\Users\dagood\.nuget\packages\microsoft.build.tasks.git\1.0.0-beta2-19367-01\build\Microsoft.Build.Tasks.Git.targets(24,5): error : Unable to locate repository with working directory that contains directory 'D:\temp\sourcelink-worktree\arcade-wt\src\Microsoft.DotNet.SignTool'. [D:\temp\sourcelink-worktree\arcade-wt\src\Microsoft.DotNet.SignTool\Microsoft.DotNet.SignTool.csproj]
C:\Users\dagood\.nuget\packages\microsoft.sourcelink.common\1.0.0-beta2-19367-01\build\Microsoft.SourceLink.Common.targets(50,5): error : Source control information is not available - the generated source link is empty. [D:\temp\sourcelink-worktree\arcade-wt\src\Microsoft.DotNet.SignTool\Microsoft.DotNet.SignTool.csproj]
C:\Users\dagood\.nuget\packages\microsoft.build.tasks.git\1.0.0-beta2-19367-01\build\Microsoft.Build.Tasks.Git.targets(24,5): error : Unable to locate repository with working directory that contains directory 'D:\temp\sourcelink-worktree\arcade-wt\src\Microsoft.DotNet.Deployment.Tasks.Links'. [D:\temp\sourcelink-worktree\arcade-wt\src\Microsoft.DotNet.Deployment.Tasks.Links\Microsoft.DotNet.Deployment.Tasks.Links.csproj]
C:\Users\dagood\.nuget\packages\microsoft.build.tasks.git\1.0.0-beta2-19367-01\build\Microsoft.Build.Tasks.Git.targets(24,5): error : Unable to locate repository with working directory that contains directory 'D:\temp\sourcelink-worktree\arcade-wt\src\Microsoft.DotNet.Arcade.Sdk'. [D:\temp\sourcelink-worktree\arcade-wt\src\Microsoft.DotNet.Arcade.Sdk\Microsoft.DotNet.Arcade.Sdk.csproj]
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