feat: keep legacy 'nightly' tag working during transition

Fall back to the moving 'nightly' tag when no immutable
vX.Y.Z-<sha>-nightly release is found, so the action keeps working
between this release and the goreleaser nightly switchover.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

__tests__/goreleaser.test.ts

@@ -104,6 +104,18 @@ describe('getCertificateIdentity', () => {
     );
   });
 
+  it('uses nightly-oss.yml@refs/heads/main for OSS legacy nightly tag', () => {
+    expect(goreleaser.getCertificateIdentity('goreleaser', 'nightly')).toEqual(
+      'https://github.com/goreleaser/goreleaser/.github/workflows/nightly-oss.yml@refs/heads/main'
+    );
+  });
+
+  it('uses nightly-pro.yml@refs/heads/main for Pro legacy nightly tag', () => {
+    expect(goreleaser.getCertificateIdentity('goreleaser-pro', 'nightly')).toEqual(
+      'https://github.com/goreleaser/goreleaser-pro-internal/.github/workflows/nightly-pro.yml@refs/heads/main'
+    );
+  });
+
   it('uses nightly-oss.yml@refs/heads/main for OSS nightly tag', () => {
     expect(goreleaser.getCertificateIdentity('goreleaser', 'v2.16.0-abc1234-nightly')).toEqual(
       'https://github.com/goreleaser/goreleaser/.github/workflows/nightly-oss.yml@refs/heads/main'

src/github.ts

@@ -34,7 +34,7 @@ export interface GitHubRelease {
 export const nightlyTagRegex = /^v\d+\.\d+\.\d+-[0-9a-f]+-nightly$/i;
 
 export const isNightlyTag = (tag: string): boolean => {
-  return nightlyTagRegex.test(tag);
+  return tag === 'nightly' || nightlyTagRegex.test(tag);
 };
 
 export const getRelease = async (distribution: string, version: string): Promise<GitHubRelease> => {
@@ -114,11 +114,15 @@ const resolveNightly = async (distribution: string): Promise<GitHubRelease> => {
   });
 
   const match = releases.find(r => nightlyTagRegex.test(r.tag_name));
-  if (!match) {
+  if (match) {
-    throw new Error(`No '<version>-<sha>-nightly' release found in ${url}`);
-  }
     core.info(`Resolved nightly to ${match.tag_name}`);
     return match;
+  }
+
+  // Fallback to the legacy moving `nightly` tag during the transition period,
+  // until goreleaser stops publishing it.
+  core.warning(`No '<version>-<sha>-nightly' release found in ${url}, falling back to 'nightly' tag`);
+  return {tag_name: 'nightly'};
 };
 
 const resolveVersion = async (distribution: string, version: string): Promise<string | null> => {