close#33086
* Add a special value for "SSH_USER" setting: `(DOER_USERNAME)`
* Improve parseRepositoryURL and add tests (now it doesn't have hard
dependency on some setting values)
Many changes are just adding "ctx" and "doer" argument to functions.
By the way, improve app.example.ini, remove all `%(key)s` syntax, it
only makes messy and no user really cares about it.
Document: https://gitea.com/gitea/docs/pulls/138
This module is merged from https://github.com/go-gitea/git which is a Go module to access Git through shell commands. Now it's a part of gitea's main repository for easier pull request.