[Github] Fetch number of commits in PR for docs action

.github/workflows/docs.yml

@@ -25,10 +25,28 @@ jobs:
  name: "Test documentation build"
  runs-on: ubuntu-latest
  steps:
- - name: Fetch LLVM sources
+ # Fetch all the commits in a pull request so that the
+ # docs-changed-subprojects step won't pull them in itself in an extremely
+ # slow manner.
+ - name: Fetch LLVM sources (PR)
+ if: ${{ github.event_name == 'pull_request' }} 
+ uses: actions/checkout@v4
+ with:
+ fetch-depth: ${{ github.event.pull_request.commits }}
+ - name: Fetch LLVM sources (push)
+ if: ${{ github.event_name == 'push' }}
  uses: actions/checkout@v4
  with:
  fetch-depth: 1
+ - name: Get subprojects that have doc changes
+ id: docs-changed-subprojects
+ uses: tj-actions/changed-files@v39
+ with:
+ files_yaml: |
+ llvm:
+ - 'llvm/docs/**'
+ clang:
+ - 'clang/docs/**'
  - name: Setup Python env
  uses: actions/setup-python@v4
  with:
@@ -41,15 +59,6 @@ jobs:
  run: |
  sudo apt-get update
  sudo apt-get install -y cmake ninja-build
- - name: Get subprojects that have doc changes
- id: docs-changed-subprojects
- uses: tj-actions/changed-files@v39
- with:
- files_yaml: |
- llvm:
- - 'llvm/docs/**'
- clang:
- - 'clang/docs/**'
  - name: Build LLVM docs
  if: steps.docs-changed-subprojects.outputs.llvm_any_changed == 'true'
  run: |