Close#13454 , Close#23255, Close#14697 (and maybe more related
issues)
Many users have the requirement to customize the git config. This PR
introduces an easy way: put the options in Gitea's app.ini
`[git.config]`, then the config options will be applied to git config.
And it can support more flexible default config values, eg: now
`diff.algorithm=histogram` by default. According to:
https://stackoverflow.com/a/32367597/4754037 , `histogram diff` is
efficient and doesn't like to cause server-side problems.
---------
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: Giteabot <teabot@gitea.io>
