feat: Flag to disable custom [Atlantis] commit messages on PR merge (#3120)

* Modify the automere commit message to include the PR number [DEVOPS-674]

* Update server/events/vcs/common/common.go

Co-authored-by: Ken Kaizu <k.kaizu38@gmail.com>

* added test for PR message func [DEVOPS-674]

---------

Co-authored-by: Ken Kaizu <k.kaizu38@gmail.com>

server/events/vcs/azuredevops_client.go

@@ -325,7 +325,7 @@ func (g *AzureDevopsClient) MergePull(pull models.PullRequest, pullOptions model
 		BypassPolicy:            new(bool),
 		BypassReason:            azuredevops.String(""),
 		DeleteSourceBranch:      &pullOptions.DeleteSourceBranchOnMerge,
-		MergeCommitMessage:      azuredevops.String(common.AutomergeCommitMsg),
+		MergeCommitMessage:      azuredevops.String(common.AutomergeCommitMsg(pull.Num)),
 		MergeStrategy:           &mcm,
 		SquashMerge:             new(bool),
 		TransitionWorkItems:     twi,

server/events/vcs/common/common.go

@@ -3,12 +3,14 @@
 package common
 
 import (
+	"fmt"
 	"math"
 )
 
-// AutomergeCommitMsg is the commit message Atlantis will use when automatically
-// merging pull requests.
-const AutomergeCommitMsg = "[Atlantis] Automatically merging after successful apply"
+// AutomergeCommitMsg returns the commit message to use when automerging.
+func AutomergeCommitMsg(pullNum int) string {
+	return fmt.Sprintf("[Atlantis] Automatically merging after successful apply: PR #%d", pullNum)
+}
 
 // SplitComment splits comment into a slice of comments that are under maxSize.
 // It appends sepEnd to all comments that have a following comment.

server/events/vcs/common/common_test.go

@@ -18,7 +18,6 @@ import (
 	"testing"
 
 	"github.com/runatlantis/atlantis/server/events/vcs/common"
-
 	. "github.com/runatlantis/atlantis/testing"
 )
 
@@ -61,3 +60,24 @@ func TestSplitComment_FourComments(t *testing.T) {
 		sepStart + comment[expMax*2:expMax*3] + sepEnd,
 		sepStart + comment[expMax*3:]}, split)
 }
+
+func TestAutomergeCommitMsg(t *testing.T) {
+	tests := []struct {
+		name    string
+		pullNum int
+		want    string
+	}{
+		{
+			name:    "Atlantis PR commit message should include PR number",
+			pullNum: 123,
+			want:    "[Atlantis] Automatically merging after successful apply: PR #123",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := common.AutomergeCommitMsg(tt.pullNum); got != tt.want {
+				t.Errorf("AutomergeCommitMsg() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

server/events/vcs/gitlab_client.go

@@ -313,7 +313,7 @@ func (g *GitlabClient) WaitForSuccessPipeline(ctx context.Context, pull models.P
 
 // MergePull merges the merge request.
 func (g *GitlabClient) MergePull(pull models.PullRequest, pullOptions models.PullRequestOptions) error {
-	commitMsg := common.AutomergeCommitMsg
+	commitMsg := common.AutomergeCommitMsg(pull.Num)
 
 	mr, err := g.GetMergeRequest(pull.BaseRepo.FullName, pull.Num)
 	if err != nil {