Fix agit checkout command line hint & fix ShowMergeInstructions checking (#31219) (#31222)

Backport #31219 by @lunny

Fix #31135 

Before
<img width="527" alt="图片"
src="https://github.com/go-gitea/gitea/assets/81045/60c07b55-3db2-4a9a-98f1-0eb72d149df2">

After
<img width="664" alt="图片"
src="https://github.com/go-gitea/gitea/assets/81045/0670ff5d-9e0b-47ac-aba4-9db9131de3b3">

Co-authored-by: Lunny Xiao <[email protected]>

Author: GiteaBot

routers/web/repo/issue.go

@@ -1791,6 +1791,7 @@ func ViewIssue(ctx *context.Context) {
 		pull.Issue = issue
 		canDelete := false
 		allowMerge := false
+		canWriteToHeadRepo := false
 
 		if ctx.IsSigned {
 			if err := pull.LoadHeadRepo(ctx); err != nil {
@@ -1811,7 +1812,7 @@ func ViewIssue(ctx *context.Context) {
 							ctx.Data["DeleteBranchLink"] = issue.Link() + "/cleanup"
 						}
 					}
-					ctx.Data["CanWriteToHeadRepo"] = true
+					canWriteToHeadRepo = true
 				}
 			}
 
@@ -1823,6 +1824,9 @@ func ViewIssue(ctx *context.Context) {
 				ctx.ServerError("GetUserRepoPermission", err)
 				return
 			}
+			if !canWriteToHeadRepo { // maintainers maybe allowed to push to head repo even if they can't write to it
+				canWriteToHeadRepo = pull.AllowMaintainerEdit && perm.CanWrite(unit.TypeCode)
+			}
 			allowMerge, err = pull_service.IsUserAllowedToMerge(ctx, pull, perm, ctx.Doer)
 			if err != nil {
 				ctx.ServerError("IsUserAllowedToMerge", err)
@@ -1835,6 +1839,8 @@ func ViewIssue(ctx *context.Context) {
 			}
 		}
 
+		ctx.Data["CanWriteToHeadRepo"] = canWriteToHeadRepo
+		ctx.Data["ShowMergeInstructions"] = canWriteToHeadRepo
 		ctx.Data["AllowMerge"] = allowMerge
 
 		prUnit, err := repo.GetUnit(ctx, unit.TypePullRequests)
@@ -1889,13 +1895,9 @@ func ViewIssue(ctx *context.Context) {
 			ctx.ServerError("LoadProtectedBranch", err)
 			return
 		}
-		ctx.Data["ShowMergeInstructions"] = true
+
 		if pb != nil {
 			pb.Repo = pull.BaseRepo
-			var showMergeInstructions bool
-			if ctx.Doer != nil {
-				showMergeInstructions = pb.CanUserPush(ctx, ctx.Doer)
-			}
 			ctx.Data["ProtectedBranch"] = pb
 			ctx.Data["IsBlockedByApprovals"] = !issues_model.HasEnoughApprovals(ctx, pb, pull)
 			ctx.Data["IsBlockedByRejection"] = issues_model.MergeBlockedByRejectedReview(ctx, pb, pull)
@@ -1906,7 +1908,6 @@ func ViewIssue(ctx *context.Context) {
 			ctx.Data["ChangedProtectedFiles"] = pull.ChangedProtectedFiles
 			ctx.Data["IsBlockedByChangedProtectedFiles"] = len(pull.ChangedProtectedFiles) != 0
 			ctx.Data["ChangedProtectedFilesNum"] = len(pull.ChangedProtectedFiles)
-			ctx.Data["ShowMergeInstructions"] = showMergeInstructions
 		}
 		ctx.Data["WillSign"] = false
 		if ctx.Doer != nil {

templates/repo/issue/view_content/pull_merge_instruction.tmpl

@@ -9,10 +9,10 @@
 	<div class="ui secondary segment">
 		{{if eq .PullRequest.Flow 0}}
 		<div>git fetch -u {{if ne .PullRequest.HeadRepo.ID .PullRequest.BaseRepo.ID}}<origin-url data-url="{{.PullRequest.HeadRepo.Link}}"></origin-url>{{else}}origin{{end}} {{.PullRequest.HeadBranch}}:{{$localBranch}}</div>
-		<div>git checkout {{$localBranch}}</div>
 		{{else}}
-		<div>git fetch -u origin {{.GetGitRefName}}:{{$localBranch}}</div>
+		<div>git fetch -u origin {{.PullRequest.GetGitRefName}}:{{$localBranch}}</div>
 		{{end}}
+		<div>git checkout {{$localBranch}}</div>
 	</div>
 	{{if .ShowMergeInstructions}}
 	<div><h3>{{ctx.Locale.Tr "repo.pulls.cmd_instruction_merge_title"}}</h3>{{ctx.Locale.Tr "repo.pulls.cmd_instruction_merge_desc"}}</div>