feat: add download-from-astral-mirror input (#897)

## Summary

Add a new boolean input `download-from-astral-mirror` (default: `true`)
that controls whether uv is downloaded from the Astral mirror or
directly from GitHub Releases.

When set to `false`, the mirror rewrite is skipped entirely and the
download goes straight to GitHub Releases.

Closes: #870

src/download/download-version.ts

@@ -36,6 +36,7 @@ export async function downloadVersion(
   checksum: string | undefined,
   githubToken: string,
   manifestUrl?: string,
+  downloadFromAstralMirror = true,
 ): Promise<{ version: string; cachedToolDir: string }> {
   const artifact = await getArtifact(version, arch, platform, manifestUrl);
 
@@ -52,7 +53,9 @@ export async function downloadVersion(
       ? checksum
       : resolveChecksum(checksum, artifact.checksum);
 
-  const mirrorUrl = rewriteToMirror(artifact.downloadUrl);
+  const mirrorUrl = downloadFromAstralMirror
+    ? rewriteToMirror(artifact.downloadUrl)
+    : undefined;
   const downloadUrl = mirrorUrl ?? artifact.downloadUrl;
 
   try {

src/setup-uv.ts

@@ -154,6 +154,7 @@ async function setupUv(
     inputs.checksum,
     inputs.githubToken,
     inputs.manifestFile,
+    inputs.downloadFromAstralMirror,
   );
 
   return {

src/utils/inputs.ts

@@ -40,6 +40,7 @@ export interface SetupInputs {
   pythonDir: string;
   githubToken: string;
   manifestFile?: string;
+  downloadFromAstralMirror: boolean;
   addProblemMatchers: boolean;
   resolutionStrategy: ResolutionStrategy;
 }
@@ -73,6 +74,8 @@ export function loadInputs(): SetupInputs {
   const pythonDir = getUvPythonDir();
   const githubToken = core.getInput("github-token");
   const manifestFile = getManifestFile();
+  const downloadFromAstralMirror =
+    core.getInput("download-from-astral-mirror") === "true";
   const addProblemMatchers = core.getInput("add-problem-matchers") === "true";
   const resolutionStrategy = getResolutionStrategy();
 
@@ -84,6 +87,7 @@ export function loadInputs(): SetupInputs {
     cachePython,
     cacheSuffix,
     checksum,
+    downloadFromAstralMirror,
     enableCache,
     githubToken,
     ignoreEmptyWorkdir,