left over branch configs

[extrawurst]

I accidentally realised that my .git/config is littered with left-over empty branch specs of already removed branches:

[branch "teest"]
[branch "fix-1047-can-pull"]
[branch "fix-1037"]
[branch "fix-747-annotated-tags"]
[branch "fix-1074-delete-tag-remote"]
[branch "test-fix-cargo-wix"]
[branch "tree-walk"]

[extrawurst]

this might be an issue with either how we miss something when deleting a local branch using the libgit2 methods or an issue in upstream libgit2 itself. detective work needed

[extrawurst]

see libgit2/libgit2#6190

[stale]

This issue has been automatically marked as stale because it has not had any activity half a year. It will be closed in 14 days if no further activity occurs. Thank you for your contributions.