build.sh: Add extra git debug output

Only when CI_DEBUG_BUILD is non-empty

overlay/usr/local/bin/build.sh

@@ -129,10 +129,16 @@ failed=
 sysinfo || true
 setup_system || die "Failed to setup system"
 
-git fetch -v "$CI_MERGE_REQUEST_PROJECT_URL" "+refs/heads/$BASEBRANCH:refs/heads/$BASEBRANCH"
-
-if [ -n "$CI_DEBUG_BUILD" ]; then
-	git log -200 --oneline --graph --decorate "$BASEBRANCH" HEAD
+git fetch -qn "$CI_MERGE_REQUEST_PROJECT_URL" \
+	"+refs/heads/$BASEBRANCH:refs/heads/$BASEBRANCH"
+
+if debugging; then
+	merge_base=$(git merge-base "$BASEBRANCH" HEAD)
+	echo "$merge_base"
+	git --version
+	git config -l
+	git tag merge-base "$merge_base" || { echo "Could not determine merge-base"; exit 50; }
+	git log --oneline --graph --decorate --all
 fi
 
 for repo in $(changed_repos); do