Handle shallow clones in merge_open_prs.sh

Add logic to handle shallow repositories in merge script

birdnet-pi/rootfs/helpers/merge_open_prs.sh

@@ -10,6 +10,12 @@ if ! git rev-parse --git-dir > /dev/null 2>&1; then
     exit 1
 fi
 
+# If this is a shallow clone, fetch enough history to compute merge bases
+if git rev-parse --is-shallow-repository >/dev/null 2>&1 && git rev-parse --is-shallow-repository | grep -q true; then
+  echo "🔄 Repository is shallow; fetching full history to enable merging…"
+  git fetch --unshallow || git fetch --deepen=100000
+fi
+
 # Get list of open, non-draft PR numbers via GitHub API
 echo "🔍 Fetching open PRs..."
 mapfile -t PRS < <(curl -s "https://api.github.com/repos/alexbelgium/BirdNET-Pi/pulls?state=open&per_page=100" \