Handle too long PR titles correctly

The CompareAndPullRequestPost handler for POST to /compare
incorrectly handles returning errors to the user. For a start
it does not set the necessary markers to switch SimpleMDE
but it also does not immediately return to the form.

This PR fixes this by setting the appropriate values, fixing
the templates and preventing the suggestion of a too long
title.

Fix go-gitea#16507

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

routers/web/repo/compare.go

@@ -567,6 +567,15 @@ func PrepareCompareDiff(
 	} else {
 		title = headBranch
 	}
+	if len(title) > 255 {
+		if ctx.Data["content"] != nil {
+			ctx.Data["content"] = fmt.Sprintf("...%s\n\n%s", title[252:], ctx.Data["content"])
+		} else {
+			ctx.Data["content"] = "..." + title[252:] + "\n"
+		}
+		title = title[:252] + "..."
+	}
+
 	ctx.Data["title"] = title
 	ctx.Data["Username"] = headUser.Name
 	ctx.Data["Reponame"] = headRepo.Name

routers/web/repo/pull.go

@@ -1001,10 +1001,14 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 	ctx.Data["Title"] = ctx.Tr("repo.pulls.compare_changes")
 	ctx.Data["PageIsComparePull"] = true
 	ctx.Data["IsDiffCompare"] = true
+	ctx.Data["IsRepoToolbarCommits"] = true
+	ctx.Data["RequireTribute"] = true
+	ctx.Data["RequireSimpleMDE"] = true
 	ctx.Data["RequireHighlightJS"] = true
 	ctx.Data["PullRequestWorkInProgressPrefixes"] = setting.Repository.PullRequest.WorkInProgressPrefixes
 	ctx.Data["IsAttachmentEnabled"] = setting.Attachment.Enabled
 	upload.AddUploadContext(ctx, "comment")
+	ctx.Data["HasIssuesOrPullsWritePermission"] = ctx.Repo.CanWrite(models.UnitTypePullRequests)
 
 	var (
 		repo        = ctx.Repo.Repository
@@ -1037,6 +1041,12 @@ func CompareAndPullRequestPost(ctx *context.Context) {
 			return
 		}
 
+		if len(form.Title) > 255 {
+			form.Content = "..." + form.Title[252:] + "\n\n" + form.Content
+			form.Title = form.Title[:252] + "..."
+		}
+		middleware.AssignForm(form, ctx.Data)
+
 		ctx.HTML(http.StatusOK, tplCompareDiff)
 		return
 	}

templates/repo/diff/compare.tmpl

@@ -176,10 +176,10 @@
 	{{if .IsNothingToCompare}}
 		{{if and $.IsSigned $.AllowEmptyPr (not .Repository.IsArchived) }}
 			<div class="ui segment">{{.i18n.Tr "repo.pulls.nothing_to_compare_and_allow_empty_pr"}}</div>
-			<div class="ui info message show-form-container">
+			<div class="ui info message show-form-container" {{if .Flash}}style="display: none"{{end}}>
 				<button class="ui button green show-form">{{.i18n.Tr "repo.pulls.new"}}</button>
 			</div>
-			<div class="pullrequest-form" style="display: none">
+			<div class="pullrequest-form" {{if not .Flash}}style="display: none"{{end}}>
 				{{template "repo/issue/new_form" .}}
 			</div>
 		{{else}}
@@ -192,7 +192,7 @@
 			</div>
 		{{else}}
 			{{if and $.IsSigned (not .Repository.IsArchived)}}
-				<div class="ui info message show-form-container">
+				<div class="ui info message show-form-container" {{if .Flash}}style="display: none"{{end}}>
 					<button class="ui button green show-form">{{.i18n.Tr "repo.pulls.new"}}</button>
 				</div>
 			{{else if .Repository.IsArchived}}
@@ -201,7 +201,7 @@
 				</div>
 			{{end}}
 			{{if $.IsSigned}}
-				<div class="pullrequest-form" style="display: none">
+				<div class="pullrequest-form" {{if not .Flash}}style="display: none"{{end}}>
 					{{template "repo/issue/new_form" .}}
 				</div>
 			{{end}}