Adopts 'unknown' as build revision in case git cannot retrieve it.

Signed-off-by: Ulysses Souza <[email protected]>

script/build/write-git-sha

@@ -2,6 +2,11 @@
 #
 # Write the current commit sha to the file GITSHA. This file is included in
 # packaging so that `docker-compose version` can include the git sha.
-#
-set -e
-git rev-parse --short HEAD > compose/GITSHA
+# sets to 'unknown' and echoes a message if the command is not successful
+
+DOCKER_COMPOSE_GITSHA="$(git rev-parse --short HEAD)"
+if [[ "${?}" != "0" ]]; then
+    echo "Couldn't get revision of the git repository. Setting to 'unknown' instead"
+    DOCKER_COMPOSE_GITSHA="unknown"
+fi
+echo "${DOCKER_COMPOSE_GITSHA}" > compose/GITSHA