new: dev: debug messages on launcher

Using ``DEBUG=1`` on binary compose docker launcher prints
pretty-printed docker command launched as well as important
system variables.

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

bin/compose

@@ -454,6 +454,17 @@ mk_docker_run_options() {
     mkdir -p "$COMPOSE_VAR"/sessions
     mv "$filename" "$dest"
     echo "$dest"
+
+    if [ "$DEBUG" ]; then
+        echo "${WHITE}Environment:${NORMAL}"
+        echo "  COMPOSE_DOCKER_IMAGE: $COMPOSE_DOCKER_IMAGE"
+        echo "  CHARM_STORE: $CHARM_STORE"
+        echo "  DATASTORE: $DATASTORE"
+        echo "  CONFIGSTORE: $CONFIGSTORE"
+        echo "  COMPOSE_VAR: $COMPOSE_VAR"
+        echo "  COMPOSE_CACHE: $COMPOSE_CACHE"
+    fi >&2
+
 }
 
 
@@ -496,6 +507,20 @@ get_tz() {
 }
 
 
+pretty_print() {
+    while [ "$#" != 0 ]; do
+        case "$1" in
+            "-v"|"-e"|"-w")
+                e "$1" "$2" "\\"$'\n'
+                shift;;
+            *)
+                e "$1 ";;
+        esac
+        shift
+    done
+}
+
+
 run() {
     local os docker_run_opts
 
@@ -519,6 +544,14 @@ run() {
 
     [ -t 0 ] && docker_run_opts+=("-i")
     [ -t 1 ] && docker_run_opts+=("-t")
+    if [ "$DEBUG" ]; then
+        echo "${WHITE}Launching:${NORMAL}"
+        echo "  docker run --rm \\"
+        pretty_print "${docker_run_opts[@]}" | sed -r 's/^/      /g' >&2
+        echo "\\"$'\n' >&2
+        echo "      ${COMPOSE_DOCKER_IMAGE} \\"
+        echo "         " "$@"
+    fi >&2
     exec docker run --rm "${docker_run_opts[@]}" "${COMPOSE_DOCKER_IMAGE}" "$@"
 }