This PR replaces all string refName as a type `git.RefName` to make the
code more maintainable.

Fix #15367
Replaces #23070 
It also fixed a bug that tags are not sync because `git remote --prune
origin` will not remove local tags if remote removed.

We in fact should use `git fetch --prune --tags origin` but not `git
remote update origin` to do the sync.

Some answer from ChatGPT as ref.

> If the git fetch --prune --tags command is not working as expected,
there could be a few reasons why. Here are a few things to check:
> 
>Make sure that you have the latest version of Git installed on your
system. You can check the version by running git --version in your
terminal. If you have an outdated version, try updating Git and see if
that resolves the issue.
> 
>Check that your Git repository is properly configured to track the
remote repository's tags. You can check this by running git config
--get-all remote.origin.fetch and verifying that it includes
+refs/tags/*:refs/tags/*. If it does not, you can add it by running git
config --add remote.origin.fetch "+refs/tags/*:refs/tags/*".
> 
>Verify that the tags you are trying to prune actually exist on the
remote repository. You can do this by running git ls-remote --tags
origin to list all the tags on the remote repository.
> 
>Check if any local tags have been created that match the names of tags
on the remote repository. If so, these local tags may be preventing the
git fetch --prune --tags command from working properly. You can delete
local tags using the git tag -d command.

---------

Co-authored-by: delvh <dev.lh@web.de>

When the base repository contains multiple branches with the same
commits as the base branch, pull requests can show a long list of
commits already in the base branch as having been added.

What this is supposed to do is exclude commits already in the base
branch. But the mechansim to do so assumed a commit only exists in a
single branch. Now use `git rev-list A B --not branchName` instead of
filtering commits afterwards.

The logic to detect if there was a force push also was wrong for
multiple branches. If the old commit existed in any branch in the base
repository it would assume there was no force push. Instead check if the
old commit is an ancestor of the new commit.

Change all license headers to comply with REUSE specification.

Fix #16132

Co-authored-by: flynnnnnnnnnn <flynnnnnnnnnn@github>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>

Follow #21464

Make all git command arguments strictly safe. Most changes are one-to-one replacing, keep all existing logic.

Follows #19266, #8553, Close #18553, now there are only three `Run..(&RunOpts{})` functions.
 * before: `stdout, err := RunInDir(path)`
 * now: `stdout, _, err := RunStdString(&git.RunOpts{Dir:path})`

This PR continues the work in #17125 by progressively ensuring that git
commands run within the request context.

This now means that the if there is a git repo already open in the context it will be used instead of reopening it.

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Some refactors related repository model

* Move more methods out of repository

* Move repository into models/repo

* Fix test

* Fix test

* some improvements

* Remove unnecessary function

Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>