perf(github): stop re-spawning the repo-identity probe every 30 seconds (#16450)

src/main/github/github-repository-identity.ts

@@ -61,6 +61,14 @@ export function ghRepoExecOptions(context: GitHubRepoContext): {
 
 const OWNER_REPO_POSITIVE_CACHE_TTL_MS = 30_000
 const OWNER_REPO_NEGATIVE_CACHE_TTL_MS = 5 * 60_000
+/**
+ * A signature-backed answer is held as long as a negative one. `git remote
+ * get-url` reads `.git/config`, and the signature covers that file plus every
+ * path it includes — so while the signature holds, a re-probe can only return
+ * what is already cached. The short TTL above is the no-signature fallback
+ * (remote runtimes, an unreadable gitdir), where nothing invalidates on change.
+ */
+const OWNER_REPO_SIGNED_CACHE_TTL_MS = 5 * 60_000
 const OWNER_REPO_CACHE_MAX_ENTRIES = 512
 
 type OwnerRepoCacheEntry = {
@@ -106,10 +114,10 @@ export async function getRemoteUrlForRepo(
 }
 
 function getOwnerRepoCacheTtl(value: OwnerRepo | null, configSignature?: string): number {
-  if (value) {
-    return OWNER_REPO_POSITIVE_CACHE_TTL_MS
+  if (configSignature) {
+    return value ? OWNER_REPO_SIGNED_CACHE_TTL_MS : OWNER_REPO_NEGATIVE_CACHE_TTL_MS
   }
-  return configSignature ? OWNER_REPO_NEGATIVE_CACHE_TTL_MS : OWNER_REPO_POSITIVE_CACHE_TTL_MS
+  return OWNER_REPO_POSITIVE_CACHE_TTL_MS
 }
 
 export async function getOwnerRepoForRemote(
@@ -135,7 +143,11 @@ export async function getOwnerRepoForRemote(
   pruneOwnerRepoCache(now)
   const cached = ownerRepoCache.get(cacheKey)
   if (cached && cached.expiresAt > now) {
-    if (cached.value === null && cached.configSignature !== undefined) {
+    // Why every signed entry, not only the negatives: a positive identity is
+    // held for the same five minutes now, so the same revalidation is what
+    // keeps a `git remote set-url` visible within one lookup rather than five
+    // minutes. The signature read is fs stat/readFile, not a Git subprocess.
+    if (cached.configSignature !== undefined) {
       const currentSignature = await readLocalGitConfigSignature(context)
       if (currentSignature !== cached.configSignature) {
         ownerRepoCache.delete(cacheKey)
@@ -203,9 +215,14 @@ async function resolveOwnerRepoForRemote(
     // Why: PR mutations need the effective host behind an SSH alias.
     const classification = await classifyGitHubOwnerRepoFromRemoteUrl(remoteUrl, context)
     if (classification.kind === 'github') {
+      // Why store the signature: without it this entry can only expire on the
+      // clock, which put a `git remote get-url` (plus its ssh-alias probe) on
+      // every PR refresh cycle — the second most frequent Git subprocess in a
+      // Windows field trace, on a host spawning Git at ~250-800ms a call.
       ownerRepoCache.set(cacheKey, {
         value: classification.ownerRepo,
-        expiresAt: now + getOwnerRepoCacheTtl(classification.ownerRepo, configSignature)
+        expiresAt: now + getOwnerRepoCacheTtl(classification.ownerRepo, configSignature),
+        ...(configSignature ? { configSignature } : {})
       })
       pruneOwnerRepoCache(now)
       return classification.ownerRepo