Allow configuring RegEx patterns for copySourcePRLabels

docs/config-file-options.md

@@ -490,11 +490,15 @@ Assign the same reviewers to the target pull request that were assigned to the o
 
 #### `copySourcePRLabels`
 
-Copies all labels from the original (source) pull request to the backport (target) pull request.
+Copies labels from the original (source) pull request to the backport (target) pull request.
+Can be either a boolean or an array of strings. When set to `true`, _all_ labels from the source PR are copied to the target PR.
+When an array of strings is configured, each string is used as a RegEx pattern and will be compared to each label of the source PR.
+If the label on the source PR matches at least one configured string, it will be copied to the target PR.
 
+Default: `false`
 ```json
 {
-  "copySourcePRLabels": false
+  "copySourcePRLabels": ["^Team:.*", "^:.*", "^>.*"]
 }
 ```
 

src/lib/cherrypickAndCreateTargetPullRequest/copySourcePullRequestLabels.ts

@@ -7,22 +7,39 @@ export async function copySourcePullRequestLabelsToTargetPullRequest(
   commits: Commit[],
   pullNumber: number,
 ) {
-  const labels = getNonBackportLabels(commits);
+  const labels = getNonBackportLabels(commits, options);
   if (labels.length > 0) {
     await addLabelsToPullRequest({ ...options, pullNumber, labels });
   }
 }
 
-function getNonBackportLabels(commits: Commit[]) {
+function getNonBackportLabels(commits: Commit[], options: ValidConfigOptions) {
   return commits.flatMap((commit) => {
     if (!commit.sourcePullRequest) {
       return [];
     }
 
     const backportLabels = commit.targetPullRequestStates.map((pr) => pr.label);
-    const labels = commit.sourcePullRequest.labels.filter(
-      (label) => !backportLabels.includes(label),
-    );
+    const labels = commit.sourcePullRequest.labels.filter((label) => {
+      // If `copySourcePRLabels` is a boolean, it must be true to reach this method.
+      // Therefore, we simply copy all labels from the source PR that aren't already on the target PR.
+      const copySourcePRLabels = options.copySourcePRLabels;
+      if (typeof copySourcePRLabels === 'boolean') {
+        return !backportLabels.includes(label);
+      }
+      // Otherwise, it's an array of regex patterns.
+      if (
+        typeof copySourcePRLabels === 'object' &&
+        copySourcePRLabels.constructor === Array
+      ) {
+        return copySourcePRLabels.some((sourceLabel) =>
+          label.match(new RegExp(sourceLabel)),
+        );
+      }
+      throw new Error(
+        'Unexpected type of copySourcePRLabels, must be boolean or array',
+      );
+    });
 
     return labels;
   });

src/options/ConfigOptions.ts

@@ -31,7 +31,7 @@ type Options = Partial<{
   cherrypickRef: boolean;
   commitConflicts: boolean;
   commitPaths: string[];
-  copySourcePRLabels: boolean;
+  copySourcePRLabels: boolean | string[];
   copySourcePRReviewers: boolean;
   details: boolean;
   dir: string;