feat(dependabot): add branch prefix to PR titles for release branches

Dependabot PRs targeting release branches currently have generic titles
that don't indicate which branch they target. Adding a
[release-vX.Y.x] prefix to commit messages makes it immediately clear
which branch a Dependabot PR is for, improving triage and review.

Ported from tektoncd/cli#3017

Signed-off-by: Shiv Verma <shverma@redhat.com>
Assisted-by: Claude Opus 4.6 (via Claude Code)

Author: pratap0007

.github/dependabot.yml

@@ -63,6 +63,8 @@ updates:
       target-branch: release-v0.80.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.80.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -85,6 +87,8 @@ updates:
       target-branch: release-v0.80.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.80.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -110,6 +114,8 @@ updates:
       target-branch: release-v0.80.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.80.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -131,6 +137,8 @@ updates:
       target-branch: release-v0.79.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.79.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -153,6 +161,8 @@ updates:
       target-branch: release-v0.79.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.79.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -178,6 +188,8 @@ updates:
       target-branch: release-v0.79.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.79.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -199,6 +211,8 @@ updates:
       target-branch: release-v0.78.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.78.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -221,6 +235,8 @@ updates:
       target-branch: release-v0.78.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.78.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -246,6 +262,8 @@ updates:
       target-branch: release-v0.78.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.78.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -267,6 +285,8 @@ updates:
       target-branch: release-v0.77.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.77.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -289,6 +309,8 @@ updates:
       target-branch: release-v0.77.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.77.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -314,6 +336,8 @@ updates:
       target-branch: release-v0.77.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.77.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -335,6 +359,8 @@ updates:
       target-branch: release-v0.76.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.76.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -357,6 +383,8 @@ updates:
       target-branch: release-v0.76.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.76.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -382,6 +410,8 @@ updates:
       target-branch: release-v0.76.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.76.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -403,6 +433,8 @@ updates:
       target-branch: release-v0.75.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.75.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -425,6 +457,8 @@ updates:
       target-branch: release-v0.75.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.75.x] '
       labels:
         - ok-to-test
         - dependencies
@@ -450,6 +484,8 @@ updates:
       target-branch: release-v0.75.x
       schedule:
         interval: weekly
+      commit-message:
+        prefix: '[release-v0.75.x] '
       labels:
         - ok-to-test
         - dependencies

hack/generate-dependabot.go

@@ -50,6 +50,11 @@ type Ecosystem struct {
 	Cooldown         *Cooldown                `yaml:"cooldown,omitempty"`
 }
 
+// CommitMessage configures the prefix for Dependabot commit messages and PR titles
+type CommitMessage struct {
+	Prefix string `yaml:"prefix"`
+}
+
 // DependabotConfig represents the generated dependabot.yml structure
 type DependabotConfig struct {
 	Version int      `yaml:"version"`
@@ -62,6 +67,7 @@ type Update struct {
 	Directory        string                   `yaml:"directory"`
 	TargetBranch     string                   `yaml:"target-branch,omitempty"`
 	Schedule         map[string]interface{}   `yaml:"schedule"`
+	CommitMessage    *CommitMessage           `yaml:"commit-message,omitempty"`
 	Labels           []string                 `yaml:"labels"`
 	Ignore           []map[string]interface{} `yaml:"ignore,omitempty"`
 	Groups           map[string]interface{}   `yaml:"groups,omitempty"`
@@ -169,6 +175,7 @@ func generateDependabotConfig(config Config) DependabotConfig {
 				Directory:        ecosystem.Directory,
 				TargetBranch:     branch,
 				Schedule:         ecosystem.Schedule,
+				CommitMessage:    &CommitMessage{Prefix: "[" + branch + "] "},
 				Labels:           ecosystem.Labels,
 				Ignore:           ignore,
 				Groups:           ecosystem.Groups,