perf(git): skip malformed remote base probes

src/main/runtime/fetch-remote-cache.test.ts

@@ -176,8 +176,17 @@ describe('OrcaRuntimeService.fetchRemoteWithCache', () => {
     expect(caches.fetchLastCompletedAt.has('/repo/cache-0::origin')).toBe(false)
   })
 
-  it.each(['main', 'a'.repeat(40), 'refs/remotes/main', ''])(
-    'does not launch Git for a base without a remote/branch separator: %s',
+  it.each([
+    'main',
+    'a'.repeat(40),
+    'refs/remotes/main',
+    '',
+    'origin/',
+    '/main',
+    'refs/remotes/origin/',
+    'refs/remotes//main'
+  ])(
+    'does not launch Git for a base without both remote and branch components: %s',
     async (base) => {
       const runtime = new OrcaRuntimeService(null)
       await expect(runtime.resolveRemoteTrackingBase('/repo/e', base)).resolves.toBeNull()

src/main/runtime/runtime-remote-fetch-controller.ts

@@ -231,7 +231,7 @@ export class RuntimeRemoteFetchController {
       ? baseBranch.slice(remoteRefPrefix.length)
       : baseBranch
     // A remote-tracking base needs both a configured remote and a branch component.
-    if (!shortBaseBranch.includes('/')) {
+    if (shortBaseBranch.indexOf('/') <= 0 || shortBaseBranch.endsWith('/')) {
       return null
     }
     let remotes: string[]