Allow custom default merge message with .gitea/default_merge_message/<merge_style>_TEMPLATE.md (#18177)

* Allow custom default merge message with .gitea/MERGE_MESSAGE_<merge_style>_TEMPLATE.md

* Some improvements

* Follow some advices

* Fix bug

* Fix bug

* Fix lint

* Fix close comment

* Fix test

* Fix and docs

* Improve codes

* Update docs and remove unnecessary variables

* return error for GetDefaultMergeMessage

* Fix test

* improve code

* ignore unknow unit type

* return error for GetDefaultMergeMessage

* Update services/pull/merge.go

* Some improvements

* Follow some advices

* Fix bug

* Fix lint

* Improve codes

* Update docs and remove unnecessary variables

* return error for GetDefaultMergeMessage

* improve code

* Handle deleted HeadRepo in GetDefaultMergeMessage

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

* Fix test

* Fix test

Co-authored-by: zeripath <art27@cantab.net>

2 files changed, 39 insertions, 16 deletions

diff --git a/routers/web/repo/issue.go b/routers/web/repo/issue.go
index 620b76f46d..7ddeb05f71 100644
--- a/routers/web/repo/issue.go
+++ b/routers/web/repo/issue.go
@@ -712,8 +712,6 @@ func RetrieveRepoMetas(ctx *context.Context, repo *repo_model.Repository, isPull
 }
 
 func getFileContentFromDefaultBranch(ctx *context.Context, filename string) (string, bool) {
-	var bytes []byte
-
 	if ctx.Repo.Commit == nil {
 		var err error
 		ctx.Repo.Commit, err = ctx.Repo.GitRepo.GetBranchCommit(ctx.Repo.Repository.DefaultBranch)
@@ -734,7 +732,7 @@ func getFileContentFromDefaultBranch(ctx *context.Context, filename string) (str
 		return "", false
 	}
 	defer r.Close()
-	bytes, err = io.ReadAll(r)
+	bytes, err := io.ReadAll(r)
 	if err != nil {
 		return "", false
 	}
@@ -1574,26 +1572,42 @@ func ViewIssue(ctx *context.Context) {
 		}
 		prConfig := prUnit.PullRequestsConfig()
 
+		var mergeStyle repo_model.MergeStyle
 		// Check correct values and select default
 		if ms, ok := ctx.Data["MergeStyle"].(repo_model.MergeStyle); !ok ||
 			!prConfig.IsMergeStyleAllowed(ms) {
 			defaultMergeStyle := prConfig.GetDefaultMergeStyle()
 			if prConfig.IsMergeStyleAllowed(defaultMergeStyle) && !ok {
-				ctx.Data["MergeStyle"] = defaultMergeStyle
+				mergeStyle = defaultMergeStyle
 			} else if prConfig.AllowMerge {
-				ctx.Data["MergeStyle"] = repo_model.MergeStyleMerge
+				mergeStyle = repo_model.MergeStyleMerge
 			} else if prConfig.AllowRebase {
-				ctx.Data["MergeStyle"] = repo_model.MergeStyleRebase
+				mergeStyle = repo_model.MergeStyleRebase
 			} else if prConfig.AllowRebaseMerge {
-				ctx.Data["MergeStyle"] = repo_model.MergeStyleRebaseMerge
+				mergeStyle = repo_model.MergeStyleRebaseMerge
 			} else if prConfig.AllowSquash {
-				ctx.Data["MergeStyle"] = repo_model.MergeStyleSquash
+				mergeStyle = repo_model.MergeStyleSquash
 			} else if prConfig.AllowManualMerge {
-				ctx.Data["MergeStyle"] = repo_model.MergeStyleManuallyMerged
-			} else {
-				ctx.Data["MergeStyle"] = ""
+				mergeStyle = repo_model.MergeStyleManuallyMerged
 			}
 		}
+
+		ctx.Data["MergeStyle"] = mergeStyle
+
+		defaultMergeMessage, err := pull_service.GetDefaultMergeMessage(ctx.Repo.GitRepo, pull, mergeStyle)
+		if err != nil {
+			ctx.ServerError("GetDefaultMergeMessage", err)
+			return
+		}
+		ctx.Data["DefaultMergeMessage"] = defaultMergeMessage
+
+		defaultSquashMergeMessage, err := pull_service.GetDefaultMergeMessage(ctx.Repo.GitRepo, pull, repo_model.MergeStyleSquash)
+		if err != nil {
+			ctx.ServerError("GetDefaultSquashMergeMessage", err)
+			return
+		}
+		ctx.Data["DefaultSquashMergeMessage"] = defaultSquashMergeMessage
+
 		if err = pull.LoadProtectedBranch(); err != nil {
 			ctx.ServerError("LoadProtectedBranch", err)
 			return
diff --git a/routers/web/repo/pull.go b/routers/web/repo/pull.go
index a0b3567738..27b61309a5 100644
--- a/routers/web/repo/pull.go
+++ b/routers/web/repo/pull.go
@@ -950,13 +950,22 @@ func MergePullRequest(ctx *context.Context) {
 		return
 	}
 
-	// set defaults to propagate needed fields
-	if err := form.SetDefaults(ctx, pr); err != nil {
-		ctx.ServerError("SetDefaults", fmt.Errorf("SetDefaults: %v", err))
-		return
+	message := strings.TrimSpace(form.MergeTitleField)
+	if len(message) == 0 {
+		var err error
+		message, err = pull_service.GetDefaultMergeMessage(ctx.Repo.GitRepo, pr, repo_model.MergeStyle(form.Do))
+		if err != nil {
+			ctx.ServerError("GetDefaultMergeMessage", err)
+			return
+		}
+	}
+
+	form.MergeMessageField = strings.TrimSpace(form.MergeMessageField)
+	if len(form.MergeMessageField) > 0 {
+		message += "\n\n" + form.MergeMessageField
 	}
 
-	if err := pull_service.Merge(pr, ctx.Doer, ctx.Repo.GitRepo, repo_model.MergeStyle(form.Do), form.HeadCommitID, form.MergeTitleField); err != nil {
+	if err := pull_service.Merge(ctx, pr, ctx.Doer, ctx.Repo.GitRepo, repo_model.MergeStyle(form.Do), form.HeadCommitID, message); err != nil {
 		if models.IsErrInvalidMergeStyle(err) {
 			ctx.Flash.Error(ctx.Tr("repo.pulls.invalid_merge_option"))
 			ctx.Redirect(issue.Link())