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

@@ -446,9 +446,22 @@ mk_docker_run_options() {
         p0 "-e" "COMPOSE_LAUNCHER_OPTS=$dest"
         p0 "-e" "COMPOSE_LAUNCHER_BIN=$COMPOSE_LAUNCHER_BIN"
     } >> "$filename"
+
     mkdir -p "$SESSION_DIR" || return 1
     mv -f "$filename" "$SESSION_DIR/$UID-$sha" || return 1
     echo "$SESSION_DIR/$UID-$sha"
+
+    if [ -n "$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"
+        echo "  SESSION_DIR: $SESSION_DIR"
+        echo "  TZ_PATH: $TZ_PATH"
+    fi >&2
 }
 
 
@@ -491,6 +504,20 @@ 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
 
@@ -514,7 +541,18 @@ run() {
 
     [ -t 0 ] && docker_run_opts+=("-i")
     [ -t 1 ] && docker_run_opts+=("-t")
-    exec docker run --rm "${docker_run_opts[@]}" "${COMPOSE_DOCKER_IMAGE}" "$@"
+
+    if [ -n "$DEBUG" ] || [ -n "$DRY_RUN" ]; then
+        debug "${WHITE}Launching:${NORMAL}"
+        echo "docker run --rm \\"
+        pretty_print "${docker_run_opts[@]}" | sed -r 's/^/    /g;s/([^\])$/\1\\\n/g'
+        echo "    ${COMPOSE_DOCKER_IMAGE} \\"
+        echo "       " "$@"
+    fi | { if [ -n "$DEBUG" ]; then sed -r 's/^/  /g'; else cat; fi } >&2
+    if [ -z "$DRY_RUN" ]; then
+        debug "${WHITE}Execution:${NORMAL}"
+        exec docker run --rm "${docker_run_opts[@]}" "${COMPOSE_DOCKER_IMAGE}" "$@"
+    fi
 }