Add options for getting the head or base branch

__mocks__/@actions/github.ts

@@ -1,7 +1,13 @@
 export const context = {
   payload: {
     pull_request: {
-      number: 123
+      number: 123,
+      head: {
+        ref: 'head-branch-name'
+      },
+      base: {
+        ref: 'base-branch-name'
+      }
     }
   },
   repo: {

__tests__/branch.test.ts

@@ -1,17 +1,40 @@
-import {checkBranch} from '../src/branch';
+import {getBranchName, checkBranch} from '../src/branch';
 import * as github from '@actions/github';
 
 jest.mock('@actions/core');
 jest.mock('@actions/github');
 
-describe('checkBranch', () => {
-  describe('when a single pattern is provided', () => {
-    beforeEach(() => {
-      github.context.payload.pull_request!.head = {
-        ref: 'test/feature/123'
-      };
+describe('getBranchName', () => {
+  describe('when the pull requests base branch is requested', () => {
+    it('returns the base branch name', () => {
+      const result = getBranchName('base');
+      expect(result).toEqual('base-branch-name');
     });
+  });
 
+  describe('when the pull requests head branch is requested', () => {
+    it('returns the head branch name', () => {
+      const result = getBranchName('head');
+      expect(result).toEqual('head-branch-name');
+    });
+  });
+
+  describe('when no branch is specified', () => {
+    it('returns the head branch name', () => {
+      const result = getBranchName('base');
+      expect(result).toEqual('base-branch-name');
+    });
+  });
+});
+
+describe('checkBranch', () => {
+  beforeEach(() => {
+    github.context.payload.pull_request!.head = {
+      ref: 'test/feature/123'
+    };
+  });
+
+  describe('when a single pattern is provided', () => {
     describe('and the pattern matches the head branch', () => {
       it('returns true', () => {
         const result = checkBranch(['^test']);
@@ -28,12 +51,6 @@ describe('checkBranch', () => {
   });
 
   describe('when multiple patterns are provided', () => {
-    beforeEach(() => {
-      github.context.payload.pull_request!.head = {
-        ref: 'test/feature/123'
-      };
-    });
-
     describe('and at least one pattern matches', () => {
       it('returns true', () => {
         const result = checkBranch(['^test/', '^feature/']);

src/branch.ts

@@ -1,17 +1,23 @@
 import * as core from '@actions/core';
 import * as github from '@actions/github';
 
-function getHeadBranchName(): string | undefined {
+type BranchBase = 'base' | 'head';
+
+export function getBranchName(branchBase?: BranchBase): string | undefined {
   const pullRequest = github.context.payload.pull_request;
   if (!pullRequest) {
     return undefined;
   }
 
-  return pullRequest.head?.ref;
+  if (branchBase === 'base') {
+    return pullRequest.base?.ref;
+  } else {
+    return pullRequest.head?.ref;
+  }
 }
 
-export function checkBranch(glob: string[]): boolean {
-  const branchName = getHeadBranchName();
+export function checkBranch(glob: string[], branchBase?: BranchBase): boolean {
+  const branchName = getBranchName(branchBase);
   if (!branchName) {
     core.debug(` no branch name`);
     return false;

src/labeler.ts

@@ -9,6 +9,8 @@ interface MatchConfig {
   all?: string[];
   any?: string[];
   branch?: string[];
+  headBranch?: string[];
+  baseBranch?: string[];
 }
 
 type StringOrMatchConfig = string | MatchConfig;
@@ -240,6 +242,18 @@ function checkMatch(changedFiles: string[], matchConfig: MatchConfig): boolean {
     }
   }
 
+  if (matchConfig.headBranch !== undefined) {
+    if (!checkBranch(matchConfig.headBranch, 'head')) {
+      return false;
+    }
+  }
+
+  if (matchConfig.baseBranch !== undefined) {
+    if (!checkBranch(matchConfig.baseBranch, 'base')) {
+      return false;
+    }
+  }
+
   return true;
 }