Support title and body query parameters for new PRs (go-gitea#34537) (go-gitea#34752)

Backport go-gitea#34537 by endo0911engineer

Co-authored-by: endo0911engineer <161911062+endo0911engineer@users.noreply.github.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

Author: 3 people

routers/web/repo/compare.go

@@ -574,7 +574,13 @@ func PrepareCompareDiff(
 
 	ctx.Data["CommitRepoLink"] = ci.HeadRepo.Link()
 	ctx.Data["AfterCommitID"] = headCommitID
-	ctx.Data["ExpandNewPrForm"] = ctx.FormBool("expand")
+
+	// follow GitHub's behavior: autofill the form and expand
+	newPrFormTitle := ctx.FormTrim("title")
+	newPrFormBody := ctx.FormTrim("body")
+	ctx.Data["ExpandNewPrForm"] = ctx.FormBool("expand") || ctx.FormBool("quick_pull") || newPrFormTitle != "" || newPrFormBody != ""
+	ctx.Data["TitleQuery"] = newPrFormTitle
+	ctx.Data["BodyQuery"] = newPrFormBody
 
 	if (headCommitID == ci.CompareInfo.MergeBase && !ci.DirectComparison) ||
 		headCommitID == ci.CompareInfo.BaseCommitID {