This is really a follow-up to
[#38148](https://github.com/go-gitea/gitea/pull/35305) , instead of
having specific mappings of options for git configurations, just honor
any user-provided gitconfig. I include a test which points out the
specific config I have which was previously not honored, but more
generally this means that gitea now only *adds* new gitconfig and never
overwrites any config provided under `[git.config]`.
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Signed-off-by: Royce Remer <royceremer@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>