fix: use workflow PR target and checkout params

Signed-off-by: Stephen L Arnold <nerdboy@gentoo.org>

.github/workflows/coverage.yml

@@ -6,11 +6,21 @@ name: Coverage
 
 on:
   workflow_dispatch:
-  pull_request:
+  pull_request_target:
+    types:
+      - opened
+      - synchronize
+      - reopened
   push:
     branches:
       - master
 
+## This workflow needs the `pull-request` permissions to work
+## Refs: https://docs.github.com/en/actions/reference/workflow-syntax-for-github-actions#permissions
+permissions:
+  pull-requests: write
+  contents: read
+
 jobs:
   pre_ci:
     name: Prepare CI environment
@@ -23,8 +33,8 @@ jobs:
     - name: Checkout Project
       uses: actions/checkout@v2
       with:
-        # We need to fetch with a depth of 2 for pull_request so we can do HEAD^2
-        fetch-depth: 2
+        ref: ${{ github.event.pull_request.head.ref }}
+        repository: ${{ github.event.pull_request.head.repo.full_name }}
 
     - name: Environment
       run: |
@@ -35,7 +45,7 @@ jobs:
       env:
         COMMIT_PUSH: ${{ github.event.head_commit.message }}
       run: |
-        COMMIT_MESSAGE="${COMMIT_PUSH:-$(git log --format=%B -n 1 HEAD^2)}"
+        COMMIT_MESSAGE="${COMMIT_PUSH:-$(git log --format=%B -n 1 HEAD)}"
         echo "::set-output name=commit_message::${COMMIT_MESSAGE}"
 
     - name: Extract branch name
@@ -131,7 +141,9 @@ jobs:
     steps:
     - uses: actions/checkout@v2
       with:
-        fetch-depth: 0
+        ref: ${{ github.event.pull_request.head.ref }}
+        repository: ${{ github.event.pull_request.head.repo.full_name }}
+
 
     - uses: actions/setup-python@v2
       with:
@@ -182,10 +194,6 @@ jobs:
     needs: [cov_data, base]
 
     steps:
-    - uses: actions/checkout@v2
-      #with:
-        #fetch-depth: 2
-
     # artifact downloaded to directory: (upload)name/file
     - uses: actions/download-artifact@v2