Tests worked fine if init.defaultBranch main was used,
but failed due to git branch reasons if master was still used.
Since we can only use init.defaultBranch if git version >= 2.28,
I also went with a template dir HEAD main tweak if lower so tests
now pass regardless of client git default branch and version.
Test: Ran tests with ~/.gitconfig:init.defaultBranch=master
Test: Ran tests with ~/.gitconfig:init.defaultBranch=main
Test: Ran tests for both code branches of git require
Change-Id: I49fa1e4ae45b8aec16a093132ee9fa466cbc11ec
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/290404
Tested-by: Fredrik de Groot <fredrik.de.groot@volvocars.com>
Reviewed-by: Mike Frysinger <vapier@google.com>
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