feat: sync forks (#2364)

This allows syncing a branch of a fork with a branch of the base repo. It looks like this:
![grafik](/attachments/4508920c-7d0b-4330-9083-e3048733e38d)
This is only possible, if the fork don't have commits that are not in the main repo.

The feature is already working, but it is missing Finetuning, a better API, translations and tests, so this is currently WIP. It is also not tested with go-git.

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## Release notes
<!--URL:https://codeberg.org/forgejo/forgejo-->
- Features
  - [PR](https://codeberg.org/forgejo/forgejo/pulls/2364): <!--number 2364 --><!--line 0 --><!--description c3luYyBmb3Jrcw==-->sync forks<!--description-->
<!--end release-notes-assistant-->

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/2364
Reviewed-by: Earl Warren <earl-warren@noreply.codeberg.org>
Co-authored-by: JakobDev <jakobdev@gmx.de>
Co-committed-by: JakobDev <jakobdev@gmx.de>

modules/git/repo_commit.go

@@ -444,10 +444,13 @@ func (repo *Repository) getCommitsBeforeLimit(id ObjectID, num int) ([]*Commit,
 
 func (repo *Repository) getBranches(commit *Commit, limit int) ([]string, error) {
 	if CheckGitVersionAtLeast("2.7.0") == nil {
-		stdout, _, err := NewCommand(repo.Ctx, "for-each-ref", "--format=%(refname:strip=2)").
-			AddOptionFormat("--count=%d", limit).
-			AddOptionValues("--contains", commit.ID.String(), BranchPrefix).
-			RunStdString(&RunOpts{Dir: repo.Path})
+		command := NewCommand(repo.Ctx, "for-each-ref", "--format=%(refname:strip=2)").AddOptionValues("--contains", commit.ID.String(), BranchPrefix)
+
+		if limit != -1 {
+			command = command.AddOptionFormat("--count=%d", limit)
+		}
+
+		stdout, _, err := command.RunStdString(&RunOpts{Dir: repo.Path})
 		if err != nil {
 			return nil, err
 		}