ci: no change-detection or reachability checkout can run into the one-minute limit (#6577)

* ci: change detection fetches the history its diffs read, not every branch and tag

The Detect changes job checked out with fetch-depth 0, which fetches all 1,400
branches and 670 tags to diff two commits; twice that stalled for the whole
minute and took a pull request out of the merge queue. It now checks out the
commit and fetches its ancestry and main without file contents.

* ci: no change-detection or reachability checkout can run into the one-minute limit

The Detect changes jobs of four workflows and the reachability job kept a
one-minute checkout limit with a retry; two of them hit it together and took a
pull request out of the merge queue. Each now has one checkout with three
minutes, change detection shares one fetch-history step, and the reachability
job, which reads only the base commit, fetches two commits deep.

.github/actions/fetch-history/action.yml

@@ -0,0 +1,11 @@
+name: Fetch history
+description: >-
+  Fetches this commit's ancestry and main without file contents, so the change-detection diffs run on a shallow
+  checkout. The diffs read no other branch or tag. Needs a checkout first.
+runs:
+  using: composite
+  steps:
+    - shell: bash
+      run: |
+        git fetch --no-tags --filter=blob:none --unshallow origin "$(git rev-parse HEAD)"
+        git fetch --no-tags --filter=blob:none origin +refs/heads/main:refs/remotes/origin/main

.github/workflows/ci.yml

@@ -39,20 +39,12 @@ jobs:
   test-reachability:
     name: Test reachability
     runs-on: ubuntu-latest
-    timeout-minutes: 4
+    timeout-minutes: 6
     steps:
-      # A history fetch now and then stalls until the job's limit; a second fetch gets through.
-      - id: checkout
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        continue-on-error: true
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+        timeout-minutes: 3
         with:
-          fetch-depth: 0
-      - if: steps.checkout.outcome != 'success'
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        with:
-          fetch-depth: 0
+          fetch-depth: 2
       - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4
         with:
           node-version: 22
@@ -73,7 +65,7 @@ jobs:
   changes:
     name: Detect changes
     runs-on: ubuntu-latest
-    timeout-minutes: 4
+    timeout-minutes: 8
     permissions:
       actions: read
       contents: read
@@ -94,18 +86,11 @@ jobs:
       # Force git-based change detection instead of the pull_request REST API.
       # The API path can fail the whole workflow on transient listFiles
       # timeouts before any real CI work starts.
-      # A history fetch now and then stalls until the job's limit; a second fetch gets through.
-      - id: checkout
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        continue-on-error: true
-        with:
-          fetch-depth: 0
-      - if: steps.checkout.outcome != 'success'
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        with:
-          fetch-depth: 0
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+        timeout-minutes: 3
+      - name: Fetch the history the diffs read
+        timeout-minutes: 2
+        uses: ./.github/actions/fetch-history
       - name: Check whether this commit already passed before a title or body edit
         id: edit
         uses: ./.github/actions/edit-already-passed

.github/workflows/player-perf.yml

@@ -21,24 +21,17 @@ jobs:
   changes:
     name: Detect changes
     runs-on: ubuntu-latest
-    timeout-minutes: 4
+    timeout-minutes: 8
     outputs:
       perf: ${{ steps.release.outputs.release_only == 'true' && 'false' || steps.filter.outputs.perf }}
     steps:
       # Force git-based change detection instead of the pull_request REST API.
       # The API path can fail the perf workflow on transient listFiles timeouts.
-      # A history fetch now and then stalls until the job's limit; a second fetch gets through.
-      - id: checkout
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        continue-on-error: true
-        with:
-          fetch-depth: 0
-      - if: steps.checkout.outcome != 'success'
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        with:
-          fetch-depth: 0
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+        timeout-minutes: 3
+      - name: Fetch the history the diffs read
+        timeout-minutes: 2
+        uses: ./.github/actions/fetch-history
       # HEAD is the PR merge ref; its first parent is the current base tip, unlike the payload's
       # base.sha, which goes stale and would count the base's newer commits as the PR's changes.
       - name: Find the pull request's current base

.github/workflows/regression.yml

@@ -39,7 +39,7 @@ jobs:
   changes:
     name: Detect changes
     runs-on: ubuntu-latest
-    timeout-minutes: 4
+    timeout-minutes: 8
     permissions:
       actions: read
       contents: read
@@ -50,18 +50,11 @@ jobs:
       # Force git-based change detection instead of the pull_request REST API.
       # The API path can fail the whole workflow on transient listFiles
       # timeouts before any regression shard even starts.
-      # A history fetch now and then stalls until the job's limit; a second fetch gets through.
-      - id: checkout
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        continue-on-error: true
-        with:
-          fetch-depth: 0
-      - if: steps.checkout.outcome != 'success'
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        with:
-          fetch-depth: 0
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+        timeout-minutes: 3
+      - name: Fetch the history the diffs read
+        timeout-minutes: 2
+        uses: ./.github/actions/fetch-history
       - name: Check whether this commit already passed before a title or body edit
         id: edit
         uses: ./.github/actions/edit-already-passed

.github/workflows/windows-render.yml

@@ -43,7 +43,7 @@ jobs:
   changes:
     name: Detect changes
     runs-on: ubuntu-latest
-    timeout-minutes: 4
+    timeout-minutes: 8
     permissions:
       actions: read
       contents: read
@@ -53,18 +53,11 @@ jobs:
       # Force git-based change detection instead of the pull_request REST API.
       # The API path can fail the workflow on transient listFiles timeouts
       # before the Windows render jobs even start.
-      # A history fetch now and then stalls until the job's limit; a second fetch gets through.
-      - id: checkout
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        continue-on-error: true
-        with:
-          fetch-depth: 0
-      - if: steps.checkout.outcome != 'success'
-        uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
-        timeout-minutes: 1
-        with:
-          fetch-depth: 0
+      - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
+        timeout-minutes: 3
+      - name: Fetch the history the diffs read
+        timeout-minutes: 2
+        uses: ./.github/actions/fetch-history
       - name: Check whether this commit already passed before a title or body edit
         id: edit
         uses: ./.github/actions/edit-already-passed