Use the type RefName for all the needed places and fix pull mirror sync bugs (#24634)

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 If you have an outdated version, try updating Git and see if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>

routers/private/hook_post_receive.go

@@ -7,7 +7,6 @@ import (
 	"fmt"
 	"net/http"
 	"strconv"
-	"strings"
 
 	issues_model "code.gitea.io/gitea/models/issues"
 	repo_model "code.gitea.io/gitea/models/repo"
@@ -47,7 +46,7 @@ func HookPostReceive(ctx *gitea_context.PrivateContext) {
 		// tags.  Updates to other refs (eg, refs/notes, refs/changes,
 		// or other less-standard refs spaces are ignored since there
 		// may be a very large number of them).
-		if strings.HasPrefix(refFullName, git.BranchPrefix) || strings.HasPrefix(refFullName, git.TagPrefix) {
+		if refFullName.IsBranch() || refFullName.IsTag() {
 			if repo == nil {
 				repo = loadRepository(ctx, ownerName, repoName)
 				if ctx.Written() {
@@ -67,7 +66,7 @@ func HookPostReceive(ctx *gitea_context.PrivateContext) {
 				RepoName:     repoName,
 			}
 			updates = append(updates, option)
-			if repo.IsEmpty && option.IsBranch() && (option.BranchName() == "master" || option.BranchName() == "main") {
+			if repo.IsEmpty && (refFullName.BranchName() == "master" || refFullName.BranchName() == "main") {
 				// put the master/main branch first
 				copy(updates[1:], updates)
 				updates[0] = option
@@ -79,7 +78,7 @@ func HookPostReceive(ctx *gitea_context.PrivateContext) {
 		if err := repo_service.PushUpdates(updates); err != nil {
 			log.Error("Failed to Update: %s/%s Total Updates: %d", ownerName, repoName, len(updates))
 			for i, update := range updates {
-				log.Error("Failed to Update: %s/%s Update: %d/%d: Branch: %s", ownerName, repoName, i, len(updates), update.BranchName())
+				log.Error("Failed to Update: %s/%s Update: %d/%d: Branch: %s", ownerName, repoName, i, len(updates), update.RefFullName.BranchName())
 			}
 			log.Error("Failed to Update: %s/%s Error: %v", ownerName, repoName, err)
 
@@ -124,7 +123,8 @@ func HookPostReceive(ctx *gitea_context.PrivateContext) {
 		newCommitID := opts.NewCommitIDs[i]
 
 		// post update for agit pull request
-		if git.SupportProcReceive && strings.HasPrefix(refFullName, git.PullPrefix) {
+		// FIXME: use pr.Flow to test whether it's an Agit PR or a GH PR
+		if git.SupportProcReceive && refFullName.IsPull() {
 			if repo == nil {
 				repo = loadRepository(ctx, ownerName, repoName)
 				if ctx.Written() {
@@ -132,9 +132,7 @@ func HookPostReceive(ctx *gitea_context.PrivateContext) {
 				}
 			}
 
-			pullIndexStr := strings.TrimPrefix(refFullName, git.PullPrefix)
-			pullIndexStr = strings.Split(pullIndexStr, "/")[0]
-			pullIndex, _ := strconv.ParseInt(pullIndexStr, 10, 64)
+			pullIndex, _ := strconv.ParseInt(refFullName.PullName(), 10, 64)
 			if pullIndex <= 0 {
 				continue
 			}
@@ -160,10 +158,8 @@ func HookPostReceive(ctx *gitea_context.PrivateContext) {
 			continue
 		}
 
-		branch := git.RefEndName(opts.RefFullNames[i])
-
 		// If we've pushed a branch (and not deleted it)
-		if newCommitID != git.EmptySHA && strings.HasPrefix(refFullName, git.BranchPrefix) {
+		if newCommitID != git.EmptySHA && refFullName.IsBranch() {
 
 			// First ensure we have the repository loaded, we're allowed pulls requests and we can get the base repo
 			if repo == nil {
@@ -197,6 +193,8 @@ func HookPostReceive(ctx *gitea_context.PrivateContext) {
 				}
 			}
 
+			branch := refFullName.BranchName()
+
 			// If our branch is the default branch of an unforked repo - there's no PR to create or refer to
 			if !repo.IsFork && branch == baseRepo.DefaultBranch {
 				results = append(results, private.HookPostReceiveBranchResult{})