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>

modules/private/hook.go

@@ -6,6 +6,7 @@ package private
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -56,6 +57,7 @@ type HookOptions struct {
 	GitPushOptions                  GitPushOptions
 	PullRequestID                   int64
 	IsDeployKey                     bool
+	IsWiki                          bool
 }
 
 // SSHLogOption ssh log options
@@ -79,6 +81,23 @@ type HookPostReceiveBranchResult struct {
 	URL     string
 }
 
+// HockProcReceiveResult represents an individual result from ProcReceive
+type HockProcReceiveResult struct {
+	Results []HockProcReceiveRefResult
+	Err     string
+}
+
+// HockProcReceiveRefResult represents an individual result from ProcReceive
+type HockProcReceiveRefResult struct {
+	OldOID       string
+	NewOID       string
+	Ref          string
+	OriginalRef  string
+	IsForcePush  bool
+	IsNotMatched bool
+	Err          string
+}
+
 // HookPreReceive check whether the provided commits are allowed
 func HookPreReceive(ctx context.Context, ownerName, repoName string, opts HookOptions) (int, string) {
 	reqURL := setting.LocalURL + fmt.Sprintf("api/internal/hook/pre-receive/%s/%s",
@@ -130,6 +149,33 @@ func HookPostReceive(ctx context.Context, ownerName, repoName string, opts HookO
 	return res, ""
 }
 
+// HookProcReceive proc-receive hook
+func HookProcReceive(ctx context.Context, ownerName, repoName string, opts HookOptions) (*HockProcReceiveResult, error) {
+	reqURL := setting.LocalURL + fmt.Sprintf("api/internal/hook/proc-receive/%s/%s",
+		url.PathEscape(ownerName),
+		url.PathEscape(repoName),
+	)
+
+	req := newInternalRequest(ctx, reqURL, "POST")
+	req = req.Header("Content-Type", "application/json")
+	req.SetTimeout(60*time.Second, time.Duration(60+len(opts.OldCommitIDs))*time.Second)
+	jsonBytes, _ := json.Marshal(opts)
+	req.Body(jsonBytes)
+	resp, err := req.Response()
+	if err != nil {
+		return nil, fmt.Errorf("Unable to contact gitea: %v", err.Error())
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, errors.New(decodeJSONError(resp).Err)
+	}
+	res := &HockProcReceiveResult{}
+	_ = json.NewDecoder(resp.Body).Decode(res)
+
+	return res, nil
+}
+
 // SetDefaultBranch will set the default branch to the provided branch for the provided repository
 func SetDefaultBranch(ctx context.Context, ownerName, repoName, branch string) error {
 	reqURL := setting.LocalURL + fmt.Sprintf("api/internal/hook/set-default-branch/%s/%s/%s",