fix(unit): resolve TestRepository host git configuration dependency

[brandtkeller]

Description

Current test logic is coupled with the hosts ~/.gitconfig. If the host has

[init]
        defaultBranch = main

Then the TestRepository unit test at src/internal/git/repository_test.go will fail.

Undetermined how to decouple this fully within go-git as of yet. Issues are unclear and mixed results as far as consuming $HOME/.gitconfig are concerned and all explicit definition of main for defaultBranch still results in the HEAD containing the hosts default branch and not the configuration.

This change re-writes the HEAD file to match the explicit InitOptions such that it will now pass when the hosts .gitconfig does not align to the original workflow.

Related Issue

Fixes #3567

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide Steps followed

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[mkcp]

LGTM