fix: allow running the action on a PR

src/action.ts

@@ -4,6 +4,7 @@ import { analyzeCommits } from '@semantic-release/commit-analyzer';
 import { generateNotes } from '@semantic-release/release-notes-generator';
 import {
   getBranchFromRef,
+  isPr,
   getCommits,
   getLatestPrereleaseTag,
   getLatestTag,
@@ -48,7 +49,8 @@ export default async function main() {
   const isPreReleaseBranch = preReleaseBranches
     .split(',')
     .some((branch) => currentBranch.match(branch));
-  const isPrerelease = !isReleaseBranch && isPreReleaseBranch;
+  const isPullRequest = isPr(GITHUB_REF);
+  const isPrerelease = !isReleaseBranch && !isPullRequest && isPreReleaseBranch;
 
   const identifier = appendToPreReleaseTag
     ? appendToPreReleaseTag
@@ -128,7 +130,13 @@ export default async function main() {
       ? `pre${bump || defaultBump}`
       : bump || defaultBump;
 
-    const incrementedVersion = inc(previousVersion, releaseType, identifier);
+    let incrementedVersion: string | null;
+
+    if (isPullRequest) {
+      incrementedVersion = inc(previousVersion, releaseType);
+    } else {
+      incrementedVersion = inc(previousVersion, releaseType, identifier);
+    }
 
     if (!incrementedVersion) {
       core.setFailed('Could not increment version.');

src/utils.ts

@@ -42,6 +42,10 @@ export function getBranchFromRef(ref: string) {
   return ref.replace('refs/heads/', '');
 }
 
+export function isPr(ref: string) {
+  return ref.includes('refs/pull/');
+}
+
 export function getLatestTag(
   tags: Tags,
   prefixRegex: RegExp,

tests/utils.test.ts

@@ -26,6 +26,23 @@ describe('utils', () => {
     expect(branch).toEqual('master');
   });
 
+  it('test if ref is PR', () => {
+    /*
+     * Given
+     */
+    const remoteRef = 'refs/pull/123/merge';
+
+    /*
+     * When
+     */
+    const isPullRequest = utils.isPr(remoteRef);
+
+    /*
+     * Then
+     */
+    expect(isPullRequest).toEqual(true);
+  });
+
   it('returns valid tags', async () => {
     /*
      * Given