feat: resolve nightly to latest vX.Y.Z-<sha>-nightly release (#558)

* feat: resolve nightly to latest vX.Y.Z-<sha>-nightly release

Query GitHub releases API to resolve the 'nightly' version input to the
latest immutable nightly tag, replacing the moving 'nightly' tag that is
being removed for supply-chain hardening.

Refs goreleaser/goreleaser#6550

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

* 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>

* test: assert isNightlyTag accepts legacy fallback

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

* fix: accept nightly tags without 'v' prefix

goreleaser-pro publishes nightly releases as e.g. 2.16.0-eaeb08c50-nightly
(no 'v' prefix). Make the nightly tag regex tolerate either form, and
split the integration tests so OSS asserts the legacy fallback while
Pro asserts the new <version>-<sha>-nightly format.

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

* Revert "fix: accept nightly tags without 'v' prefix"

The missing 'v' prefix on the goreleaser-pro nightly was a release
mistake; new nightlies will keep the 'v' prefix.

This reverts commit 7673f7f.

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

* ci: pass GITHUB_TOKEN to tests

The new nightly resolution hits api.github.com/repos/.../releases,
which is rate-limited for unauthenticated requests.

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

* docs: note GITHUB_TOKEN need for nightly resolution

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

---------

Signed-off-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/github.ts

@@ -30,6 +30,13 @@ export interface GitHubRelease {
   tag_name: string;
 }
 
+// Matches the new-style nightly release tag pattern: vX.Y.Z-<sha>-nightly
+export const nightlyTagRegex = /^v\d+\.\d+\.\d+-[0-9a-f]+-nightly$/i;
+
+export const isNightlyTag = (tag: string): boolean => {
+  return tag === 'nightly' || nightlyTagRegex.test(tag);
+};
+
 export const getRelease = async (distribution: string, version: string): Promise<GitHubRelease> => {
   if (version === 'latest') {
     core.warning("You are using 'latest' as default version. Will lock to '~> v2'.");
@@ -40,7 +47,7 @@ export const getRelease = async (distribution: string, version: string): Promise
 
 export const getReleaseTag = async (distribution: string, version: string): Promise<GitHubRelease> => {
   if (version === 'nightly') {
-    return {tag_name: version};
+    return resolveNightly(distribution);
   }
 
   // If version is a specific version (not a range), skip the JSON check
@@ -81,6 +88,43 @@ export const getReleaseTag = async (distribution: string, version: string): Prom
   throw new Error(`Cannot find GoReleaser release ${version} in ${url}`);
 };
 
+// resolveNightly looks up the latest immutable nightly release of the form
+// `vX.Y.Z-<sha>-nightly` on the GitHub releases of the given distribution.
+const resolveNightly = async (distribution: string): Promise<GitHubRelease> => {
+  const url = `https://api.github.com/repos/goreleaser/${distribution}/releases?per_page=100`;
+  core.debug(`Resolving latest nightly release from ${url}`);
+
+  const releases = await withRetry(async () => {
+    const http: httpm.HttpClient = new httpm.HttpClient('goreleaser-action');
+    const headers: {[name: string]: string} = {
+      Accept: 'application/vnd.github+json',
+      'X-GitHub-Api-Version': '2022-11-28'
+    };
+    const token = process.env.GITHUB_TOKEN;
+    if (token) {
+      headers['Authorization'] = `Bearer ${token}`;
+    }
+    const resp: httpm.HttpClientResponse = await http.get(url, headers);
+    const body = await resp.readBody();
+    const statusCode = resp.message.statusCode || 500;
+    if (statusCode >= 400) {
+      throw new Error(`Failed to list releases from ${url} with status code ${statusCode}: ${body}`);
+    }
+    return <Array<GitHubRelease>>JSON.parse(body);
+  });
+
+  const match = releases.find(r => nightlyTagRegex.test(r.tag_name));
+  if (match) {
+    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> => {
   const allTags: Array<string> | null = await getAllTags(distribution);
   if (!allTags) {