Merge pull request #2500 from dokku/2479-jg-suppress-output-on-submodule-success

Suppress output unless the `git submodule update` call fails

plugins/git/functions

@@ -28,7 +28,7 @@ git_build_app_repo() {
   git remote add origin "$DOKKU_ROOT/$APP" &> /dev/null
   git fetch --depth=1 origin "refs/tags/$TMP_TAG" &> /dev/null
   git reset --hard FETCH_HEAD &> /dev/null
-  git submodule update --init --recursive &> /dev/null
+  suppress_output git submodule update --init --recursive
   GIT_DIR="$DOKKU_ROOT/$APP" git tag -d "$TMP_TAG" &> /dev/null || true
   find -name .git -prune -exec rm -rf {} \; > /dev/null
 
@@ -41,6 +41,20 @@ git_build_app_repo() {
   fi
 }
 
+suppress_output() {
+  declare desc="suppress all output from a given command unless there is an error"
+  local TMP_COMMAND_OUTPUT
+  TMP_COMMAND_OUTPUT=$(mktemp "/tmp/${FUNCNAME[0]}.XXXX")
+  trap 'rm -rf "$TMP_COMMAND_OUTPUT" > /dev/null' RETURN INT TERM EXIT
+
+  "$@" > "$TMP_COMMAND_OUTPUT" 2>&1 || {
+    local exit_code="$?"
+    cat "$TMP_COMMAND_OUTPUT"
+    return "$exit_code"
+  }
+  return 0
+}
+
 git_hook_cmd() {
   declare desc="kick off receive-app trigger from git prereceive hook"
   local cmd="git-hook"