[3.15] gh-151365: Temporarily downgrade Git to prevent fatal error (GH-155495) (#155532)

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: miss-islington

.github/workflows/reusable-check-html-ids.yml

@@ -20,6 +20,13 @@ jobs:
         with:
           persist-credentials: false
           ref: ${{ github.event.pull_request.head.sha }}
+      - name: 'Downgrade Git'
+        # Temporarily downgrade to 2.43 until 2.55 is in the runner image,
+        # to avoid "fatal: shallow file has changed since we read it" bug.
+        # See https://github.com/python/cpython/issues/151365.
+        run: |
+          sudo apt-get install -y --allow-downgrades 'git=1:2.43.*' 'git-man=1:2.43.*'
+          git --version
       - name: 'Find merge base'
         id: merge-base
         run: |

.github/workflows/reusable-context.yml

@@ -94,6 +94,15 @@ jobs:
             || ''
           }}
 
+    - name: 'Downgrade Git'
+      # Temporarily downgrade to 2.43 until 2.55 is in the runner image,
+      # to avoid "fatal: shallow file has changed since we read it" bug.
+      # See https://github.com/python/cpython/issues/151365.
+      if: github.event_name == 'pull_request'
+      run: |
+        sudo apt-get install -y --allow-downgrades 'git=1:2.43.*' 'git-man=1:2.43.*'
+        git --version
+
     # Adapted from https://github.com/actions/checkout/issues/520#issuecomment-1167205721
     - name: Fetch commits to get branch diff
       if: github.event_name == 'pull_request'

.github/workflows/reusable-docs.yml

@@ -47,6 +47,14 @@ jobs:
             && github.event.pull_request.head.sha
             || ''
           }}
+    - name: 'Downgrade Git'
+      # Temporarily downgrade to 2.43 until 2.55 is in the runner image,
+      # to avoid "fatal: shallow file has changed since we read it" bug.
+      # See https://github.com/python/cpython/issues/151365.
+      if: github.event_name == 'pull_request'
+      run: |
+        sudo apt-get install -y --allow-downgrades 'git=1:2.43.*' 'git-man=1:2.43.*'
+        git --version
     # Adapted from https://github.com/actions/checkout/issues/520#issuecomment-1167205721
     - name: 'Fetch commits to get branch diff'
       if: github.event_name == 'pull_request'