Add agit flow support in gitea (#14295)

* feature: add agit flow support

ref: https://git-repo.info/en/2020/03/agit-flow-and-git-repo/

example:

```Bash
git checkout -b test
echo "test" >> README.md
git commit -m "test"
git push origin HEAD:refs/for/master -o topic=test
```

Signed-off-by: a1012112796 <1012112796@qq.com>

* fix lint

* simplify code add fix some nits

* update merge help message

* Apply suggestions from code review. Thanks @jiangxin

* add forced-update message

* fix lint

* splite writePktLine

* add refs/for/<target-branch>/<topic-branch> support also

* Add test code add fix api

* fix lint

* fix test

* skip test if git version < 2.29

* try test with git 2.30.1

* fix permission check bug

* fix some nit

* logic implify and test code update

* fix bug

* apply suggestions from code review

* prepare for merge

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

* fix permission check bug

- test code update
- apply suggestions from code review @zeripath

Signed-off-by: a1012112796 <1012112796@qq.com>

* fix bug when target branch isn't exist

* prevent some special push and fix some nits

* fix lint

* try splite

* Apply suggestions from code review

- fix permission check
- handle user rename

* fix version negotiation

* remane

* fix template

* handle empty repo

* ui: fix  branch link under the title

* fix nits

Co-authored-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

1 files changed, 19 insertions, 1 deletions

diff --git a/modules/convert/pull.go b/modules/convert/pull.go
index 8bdf17a049..6c5d15c82e 100644
--- a/modules/convert/pull.go
+++ b/modules/convert/pull.go
@@ -95,7 +95,25 @@ func ToAPIPullRequest(pr *models.PullRequest) *api.PullRequest {
 		}
 	}
 
-	if pr.HeadRepo != nil {
+	if pr.Flow == models.PullRequestFlowAGit {
+		gitRepo, err := git.OpenRepository(pr.BaseRepo.RepoPath())
+		if err != nil {
+			log.Error("OpenRepository[%s]: %v", pr.GetGitRefName(), err)
+			return nil
+		}
+		defer gitRepo.Close()
+
+		apiPullRequest.Head.Sha, err = gitRepo.GetRefCommitID(pr.GetGitRefName())
+		if err != nil {
+			log.Error("GetRefCommitID[%s]: %v", pr.GetGitRefName(), err)
+			return nil
+		}
+		apiPullRequest.Head.RepoID = pr.BaseRepoID
+		apiPullRequest.Head.Repository = apiPullRequest.Base.Repository
+		apiPullRequest.Head.Name = ""
+	}
+
+	if pr.HeadRepo != nil && pr.Flow == models.PullRequestFlowGithub {
 		apiPullRequest.Head.RepoID = pr.HeadRepo.ID
 		apiPullRequest.Head.Repository = ToRepo(pr.HeadRepo, models.AccessModeNone)