Detect merge commits (as in PRs) and switch to first parent if so

.github/workflows/render.yml

@@ -48,17 +48,6 @@ jobs:
           echo OUTPUT_FILENAME="${filename}" >> "$GITHUB_OUTPUT"
           echo output filename: ${filename}
 
-      # For pull requests, check out the head ref of the source branch from the source repo.
-      - name: Checkout
-        if: inputs.workflow == 'pr'
-        uses: actions/checkout@v4
-        with:
-          ref: ${{ github.head_ref }}
-          repository: ${{ github.event.pull_request.head.repo.full_name }}
-          fetch-depth: 0
-          fetch-tags: true
-      # For other workflows, check out the requested revision (which defaults to
-      # head of the default branch).
       - name: Checkout
         if: inputs.workflow != 'pr'
         uses: actions/checkout@v4

build.sh

@@ -245,6 +245,17 @@ fi
 # figure out git version and revision if needed.
 EXTRA_PANDOC_OPTIONS=""
 if test "${DO_GITVERSION}" == "yes"; then
+	# If HEAD is a merge commit, go to the first parent.
+	if $(git rev-parse HEAD^2 >/dev/null 2>/dev/null); then
+		parent1=$(git rev-parse HEAD^1 2>/dev/null)
+		parent2=$(git rev-parse HEAD^2 2>/dev/null)
+		echo "Merge commit detected:"
+		echo "1: $parent1"
+		echo "2: $parent2"
+		echo "Checking out $parent1."
+		git checkout $parent1
+	fi
+
 	# TODO: Should we fail if dirty?
 	raw_version="$(git describe --always --tags)"
 	echo "Git version: ${raw_version}"