Reintroduce squash merge default comment as a config setting (#16134)

* Reinstate most of commit 09304db9a5

* Move the behaviour behind a config setting

* Also fix the initial #12365

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -94,10 +94,11 @@ Values containing `#` or `;` must be quoted using `` ` `` or `"""`.
 - `REOPEN_KEYWORDS`: **reopen**, **reopens**, **reopened**: List of keywords used in Pull Request comments to automatically reopen
  a related issue
 - `DEFAULT_MERGE_MESSAGE_COMMITS_LIMIT`: **50**: In the default merge message for squash commits include at most this many commits. Set to `-1` to include all commits
-- `DEFAULT_MERGE_MESSAGE_SIZE`: **5120**: In the default merge message for squash commits limit the size of the commit messages. Set to `-1` to have no limit.
+- `DEFAULT_MERGE_MESSAGE_SIZE`: **5120**: In the default merge message for squash commits limit the size of the commit messages. Set to `-1` to have no limit. Only used if `POPULATE_SQUASH_COMMENT_WITH_COMMIT_MESSAGES` is `true`.
 - `DEFAULT_MERGE_MESSAGE_ALL_AUTHORS`: **false**: In the default merge message for squash commits walk all commits to include all authors in the Co-authored-by otherwise just use those in the limited list
 - `DEFAULT_MERGE_MESSAGE_MAX_APPROVERS`: **10**: In default merge messages limit the number of approvers listed as `Reviewed-by:`. Set to `-1` to include all.
 - `DEFAULT_MERGE_MESSAGE_OFFICIAL_APPROVERS_ONLY`: **true**: In default merge messages only include approvers who are officially allowed to review.
+- `POPULATE_SQUASH_COMMENT_WITH_COMMIT_MESSAGES`: **false**: In default squash-merge messages include the commit message of all commits comprising the pull request.
 
 ### Repository - Issue (`repository.issue`)
 

modules/setting/repository.go

@@ -78,6 +78,7 @@ var (
 			DefaultMergeMessageAllAuthors            bool
 			DefaultMergeMessageMaxApprovers          int
 			DefaultMergeMessageOfficialApproversOnly bool
+			PopulateSquashCommentWithCommitMessages  bool
 		} `ini:"repository.pull-request"`
 
 		// Issue Setting
@@ -199,6 +200,7 @@ var (
 			DefaultMergeMessageAllAuthors            bool
 			DefaultMergeMessageMaxApprovers          int
 			DefaultMergeMessageOfficialApproversOnly bool
+			PopulateSquashCommentWithCommitMessages  bool
 		}{
 			WorkInProgressPrefixes: []string{"WIP:", "[WIP]"},
 			// Same as GitHub. See
@@ -210,6 +212,7 @@ var (
 			DefaultMergeMessageAllAuthors:            false,
 			DefaultMergeMessageMaxApprovers:          10,
 			DefaultMergeMessageOfficialApproversOnly: true,
+			PopulateSquashCommentWithCommitMessages:  false,
 		},
 
 		// Issue settings

services/pull/pull.go

@@ -570,16 +570,44 @@ func GetSquashMergeCommitMessages(pr *models.PullRequest) string {
 	authors := make([]string, 0, list.Len())
 	stringBuilder := strings.Builder{}
 
-	stringBuilder.WriteString(pr.Issue.Content)
-	if stringBuilder.Len() > 0 {
-		stringBuilder.WriteRune('\n')
-		stringBuilder.WriteRune('\n')
+	if !setting.Repository.PullRequest.PopulateSquashCommentWithCommitMessages {
+		stringBuilder.WriteString(pr.Issue.Content)
+		if stringBuilder.Len() > 0 {
+			stringBuilder.WriteRune('\n')
+			stringBuilder.WriteRune('\n')
+		}
 	}
 
 	// commits list is in reverse chronological order
 	element := list.Back()
 	for element != nil {
 		commit := element.Value.(*git.Commit)
+
+		if setting.Repository.PullRequest.PopulateSquashCommentWithCommitMessages {
+			maxSize := setting.Repository.PullRequest.DefaultMergeMessageSize
+			if maxSize < 0 || stringBuilder.Len() < maxSize {
+				var toWrite []byte
+				if element == list.Back() {
+					toWrite = []byte(strings.TrimPrefix(commit.CommitMessage, pr.Issue.Title))
+				} else {
+					toWrite = []byte(commit.CommitMessage)
+				}
+
+				if len(toWrite) > maxSize-stringBuilder.Len() && maxSize > -1 {
+					toWrite = append(toWrite[:maxSize-stringBuilder.Len()], "..."...)
+				}
+				if _, err := stringBuilder.Write(toWrite); err != nil {
+					log.Error("Unable to write commit message Error: %v", err)
+					return ""
+				}
+
+				if _, err := stringBuilder.WriteRune('\n'); err != nil {
+					log.Error("Unable to write commit message Error: %v", err)
+					return ""
+				}
+			}
+		}
+
 		authorString := commit.Author.String()
 		if !authorsMap[authorString] && authorString != posterSig {
 			authors = append(authors, authorString)