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.

<!--start release-notes-assistant-->

## 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/commit_test.go

@@ -5,6 +5,7 @@ package git
 
 import (
 	"path/filepath"
+	"slices"
 	"strings"
 	"testing"
 
@@ -370,6 +371,23 @@ func TestParseCommitRenames(t *testing.T) {
 	}
 }
 
+func TestGetAllBranches(t *testing.T) {
+	bareRepo1Path := filepath.Join(testReposDir, "repo1_bare")
+
+	bareRepo1, err := openRepositoryWithDefaultContext(bareRepo1Path)
+	require.NoError(t, err)
+
+	commit, err := bareRepo1.GetCommit("95bb4d39648ee7e325106df01a621c530863a653")
+	require.NoError(t, err)
+
+	branches, err := commit.GetAllBranches()
+	require.NoError(t, err)
+
+	slices.Sort(branches)
+
+	assert.Equal(t, []string{"branch1", "branch2", "master"}, branches)
+}
+
 func Test_parseSubmoduleContent(t *testing.T) {
 	submoduleFiles := []struct {
 		fileContent  string