Removed `gitrepo.RunCmd*` functions, because gitcmd.Command works with
Repository directly.
Move some "local filesystem" related function into "localfs.go"
Refactor Git command functions to use WithXXX methods instead of
exposing RunOpts.
This change simplifies reuse across gitrepo and improves consistency,
encapsulation, and maintainability of command options.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
