Bail out of update-version script when commit hash already matches

update-version

@@ -33,6 +33,27 @@ fi
 SRCDIR="$(cd "$(dirname "$0")"; pwd)"
 SPEC="${SRCDIR}/gn.spec"
 
+SPEC_COMMIT="$(
+  awk '/^%global[[:blank:]]+commit[[:blank:]]+[[:xdigit:]]{40}[[:blank:]]*$/ {
+    print $3; exit
+  }' "${SPEC}"
+)"
+
+check_equal_commits() {
+  if [ "${1}" = "${SPEC_COMMIT}" ]
+  then
+    cat 1>&2 <<EOF
+Spec file is already up to date at ${SPEC_COMMIT}.
+EOF
+    exit
+  fi
+}
+
+if echo "${COMMIT}" | grep -E '^[[:xdigit:]]{40}$' >/dev/null
+then
+  check_equal_commits "${COMMIT}"
+fi
+
 tmpd="$(mktemp -d)"
 trap "rm -rf '${tmpd}'" INT TERM EXIT
 
@@ -42,6 +63,7 @@ cd gn
 if ! echo "${COMMIT}" | grep -E '^[[:xdigit:]]{40}$' >/dev/null
 then
   COMMIT="$(git rev-parse "${COMMIT}")"
+  check_equal_commits "${COMMIT}"
 fi
 git checkout "${COMMIT}"
 python3 './build/gen.py'