Fix gitFetch not updating FETCH_HEAD

src/executil.ts

@@ -43,11 +43,13 @@ export async function gitClone(gitDir: string, gitRepo: string, workTree: string
   await git(args);
 }
 
-export async function gitFetch(gitDir: string) {
+export async function gitFetch(gitDir: string, ref: string) {
   let args: string[] = [
     `--git-dir=${gitDir}`,
     'fetch',
     '--depth=1',
+    'origin',
+    ref,
   ];
   await git(args);
 }

src/installer.ts

@@ -85,7 +85,7 @@ async function acquireGo(version: string, gotipRef: string, bootstrapGo: string)
         workTree = '';
 
         // Cache hit for git dir, fetch new commits from upstream.
-        await executil.gitFetch(gitDir);
+        await executil.gitFetch(gitDir, gotipRef);
 
         // Extract latest commit hash.
         commitHash = await executil.gitRevParse(gitDir, 'FETCH_HEAD');