git repository mirror with detached head causes error: GH002

The following code is running in an Azure Pipeline to mirror the source to another git repository.

git remote add --mirror=fetch mirror MIRROR_REPO

git push mirror --progress --prune +refs/remotes/origin/*:refs/heads/* +refs/tags/*:refs/tags/*

When the agent runs it checks out the code at a specific commit which results in a detached head which has the name of the commit SHA. This are logs produced by the agent:

 * [new ref]           6ADFB183A4A2C94A2F92DAB5ADE762A47889A5A1 -> origin/6ADFB183A4A2C94A2F92DAB5ADE762A47889A5A1
git checkout --progress --force 6ADFB183A4A2C94A2F92DAB5ADE762A47889A5A1
Note: switching to '6ADFB183A4A2C94A2F92DAB5ADE762A47889A5A1'

I guess that's the reason the git push mirror command fails with the following error:

remote: error: GH002: Sorry, branch or tag names consisting of 40 hex characters are not allowed.        
remote: error: Invalid branch or tag name "6ADFB183A4A2C94A2F92DAB5ADE762A47889A5A1"   

I'm looking for a method to push all branches and tags from my source repository to my mirror repository every time the pipeline runs.

Thanks!

remote: error: GH002: Sorry, branch or tag names consisting of 40 hex characters are not allowed.

Based on my test, I could reproduce the same issue.

In azure devops default checkout step, it will set the commitid as the [New Ref]. Since this is the default step, we cannot interfere with how it works.

For a workaround, you could skip the default checkout step(- checkout: none) and run the git command to checkout all branches and tags.

Here is my sample:

steps:
- checkout: none

- task: PowerShell@2
  inputs:
    targetType: 'inline'
    script: |
      git clone --mirror  sourcerepo

      cd $(build.sourcesdirectory)\reponame
      
      git remote add --mirror=fetch mirror MIRROR_REPO
      
      git push mirror --progress --prune +refs/heads/*:refs/heads/* +refs/tags/*:refs/tags/*

Then it will push all branches and tags to Github successfully.