Improve pull request command line instructions (#27778)

* Show checkout instructions also when there is no permission to push,
for anyone who wants to locally test the changes.
* First checkout the branch exactly as is, without immediately having to
solve merge conflicts. Leave this to the merge step, since it's often
convenient to test a change without worrying about this.
* Use `git fetch -u`, so an existing local branch is updated when
re-testing the same pull request. But not the more risky `git fetch -f`
in to handle force pushes, as we don't want to accidentally overwrite
important local changes.
* Show different merge command depending on the chosen merge style,
interactively updated.

2 files changed, 38 insertions, 12 deletions

diff --git a/templates/repo/issue/view_content/pull.tmpl b/templates/repo/issue/view_content/pull.tmpl
index a4f7ede74d..2fed5848d5 100644
--- a/templates/repo/issue/view_content/pull.tmpl
+++ b/templates/repo/issue/view_content/pull.tmpl
@@ -372,8 +372,8 @@
 				</div>
 			{{end}}
 
-			{{if and .ShowMergeInstructions .Issue.PullRequest.HeadRepo (not .Issue.PullRequest.HasMerged) (not .Issue.IsClosed)}}
-				{{template "repo/issue/view_content/pull_merge_instruction" .Issue.PullRequest}}
+			{{if and .Issue.PullRequest.HeadRepo (not .Issue.PullRequest.HasMerged) (not .Issue.IsClosed)}}
+				{{template "repo/issue/view_content/pull_merge_instruction" dict "PullRequest" .Issue.PullRequest "ShowMergeInstructions" .ShowMergeInstructions}}
 			{{end}}
 		</div>
 	</div>
diff --git a/templates/repo/issue/view_content/pull_merge_instruction.tmpl b/templates/repo/issue/view_content/pull_merge_instruction.tmpl
index b1b52645e0..3dab44710e 100644
--- a/templates/repo/issue/view_content/pull_merge_instruction.tmpl
+++ b/templates/repo/issue/view_content/pull_merge_instruction.tmpl
@@ -1,19 +1,45 @@
 <div class="divider"></div>
-<div class="instruct-toggle"> {{ctx.Locale.Tr "repo.pulls.merge_instruction_hint" | Safe}} </div>
+<div class="instruct-toggle"> {{ctx.Locale.Tr "repo.pulls.cmd_instruction_hint" | Safe}} </div>
 <div class="instruct-content gt-mt-3 gt-hidden">
-	<div><h3 class="gt-dib">{{ctx.Locale.Tr "step1"}}</h3> {{ctx.Locale.Tr "repo.pulls.merge_instruction_step1_desc"}}</div>
+	<div><h3>{{ctx.Locale.Tr "repo.pulls.cmd_instruction_checkout_title"}}</h3>{{ctx.Locale.Tr "repo.pulls.cmd_instruction_checkout_desc"}}</div>
+	{{$localBranch := .PullRequest.HeadBranch}}
+	{{if ne .PullRequest.HeadRepo.ID .PullRequest.BaseRepo.ID}}
+		{{$localBranch = print .PullRequest.HeadRepo.OwnerName "-" .PullRequest.HeadBranch}}
+	{{end}}
 	<div class="ui secondary segment">
-		{{if eq .Flow 0}}
-		<div>git checkout -b {{if ne .HeadRepo.ID .BaseRepo.ID}}{{.HeadRepo.OwnerName}}-{{end}}{{.HeadBranch}} {{.BaseBranch}}</div>
-		<div>git pull {{if ne .HeadRepo.ID .BaseRepo.ID}}<gitea-origin-url data-url="{{.HeadRepo.Link}}"></gitea-origin-url>{{else}}origin{{end}} {{.HeadBranch}}</div>
+		{{if eq .PullRequest.Flow 0}}
+		<div>git fetch -u {{if ne .PullRequest.HeadRepo.ID .PullRequest.BaseRepo.ID}}<gitea-origin-url data-url="{{.PullRequest.HeadRepo.Link}}"></gitea-origin-url>{{else}}origin{{end}} {{.PullRequest.HeadBranch}}:{{$localBranch}}</div>
+		<div>git checkout {{$localBranch}}</div>
 		{{else}}
-		<div>git fetch origin {{.GetGitRefName}}:{{.HeadBranch}}</div>
+		<div>git fetch -u origin {{.GetGitRefName}}:{{$localBranch}}</div>
 		{{end}}
 	</div>
-	<div><h3 class="gt-dib">{{ctx.Locale.Tr "step2"}}</h3> {{ctx.Locale.Tr "repo.pulls.merge_instruction_step2_desc"}}</div>
+	{{if .ShowMergeInstructions}}
+	<div><h3>{{ctx.Locale.Tr "repo.pulls.cmd_instruction_merge_title"}}</h3>{{ctx.Locale.Tr "repo.pulls.cmd_instruction_merge_desc"}}</div>
 	<div class="ui secondary segment">
-		<div>git checkout {{.BaseBranch}}</div>
-		<div>git merge --no-ff {{if ne .HeadRepo.ID .BaseRepo.ID}}{{.HeadRepo.OwnerName}}-{{end}}{{.HeadBranch}}</div>
-		<div>git push origin {{.BaseBranch}}</div>
+		<div data-pull-merge-style="merge">
+			<div>git checkout {{.PullRequest.BaseBranch}}</div>
+			<div>git merge --no-ff {{$localBranch}}</div>
+		</div>
+		<div class="gt-hidden" data-pull-merge-style="rebase">
+			<div>git checkout {{.PullRequest.BaseBranch}}</div>
+			<div>git merge --ff-only {{$localBranch}}</div>
+		</div>
+		<div class="gt-hidden" data-pull-merge-style="rebase-merge">
+			<div>git checkout {{$localBranch}}</div>
+			<div>git rebase {{.PullRequest.BaseBranch}}</div>
+			<div>git checkout {{.PullRequest.BaseBranch}}</div>
+			<div>git merge --no-ff {{$localBranch}}</div>
+		</div>
+		<div class="gt-hidden" data-pull-merge-style="squash">
+			<div>git checkout {{.PullRequest.BaseBranch}}</div>
+			<div>git merge --squash {{$localBranch}}</div>
+		</div>
+		<div class="gt-hidden" data-pull-merge-style="manually-merged">
+			<div>git checkout {{.PullRequest.BaseBranch}}</div>
+			<div>git merge {{$localBranch}}</div>
+		</div>
+		<div>git push origin {{.PullRequest.BaseBranch}}</div>
 	</div>
+	{{end}}
 </div>