[Bug] Build fail when building a detached head

[Evangelink]

Describe the bug

I have setup my projects to use GitVersions and as soon as I try to build a commit from history (detached head), build fails with

Severity	Code	Description	Project	File	Line	Suppression State
Error	MSB3073	The command ""C:\Users\XXX\.nuget\packages\gitversion.msbuild\5.6.9\tools\net48/gitversion.exe" "C:\Src\YYY" -output file -outputfile obj\gitversion.json" exited with code 1.	YYY	C:\Users\XXX\.nuget\packages\gitversion.msbuild\5.6.9\tools\GitVersion.MsBuild.targets	9	

Expected Behavior

I should be able to get back to any commit and simply build my solution.

Actual Behavior

Build fails, I have to comment the nuget from all my projects and rebuild.

Steps to Reproduce

1. Create a simple project
2. Add GitVersion.MsBuild
3. Commit some code
4. Commit something else
5. Get back to previous commit
6. Build the solution, the solution fails

My GitVersion.yml:

assembly-versioning-scheme: MajorMinorPatch
mode: ContinuousDelivery
next-version: 1.0.0
branches: {}
ignore:
  sha: []
merge-message-formats: {}

Context

I am trying to see on which commit a bug was introduced.

Your Environment

• Version Used: 5.6.9
• Operating System and version (Windows 10, Ubuntu 18.04): Windows 10

[asbjornu]

Detached head is not supported.

[Evangelink]

Hi @asbjornu,

Thanks for the link!

I understand that a detached head makes it impossible to determine correctly a version but having build failures when looking at the history is pretty annoying. Would it be possible to consider avoiding a hard-failure or introducing some option to only warn and continue with a fallback version? I can understand the failure might be interesting for some contexts but I fail to see it useful when recompiling past versions of the code.

I am willing to help if you think that's something that could be useful.

[asbjornu]

I would accept a pull request that changed the current behavior as long as it doesn't break any other tests.