docker_build: add throbber

As the cqfd --init command is going, in the future, to be ran
automatically, work has been done to make it less instrusive.

Rather than showing all of the Docker log, it just shows a throbber
with the current step status, and shows the full log only if the
docker build command failed.

cqfd

@@ -109,13 +109,64 @@ die() {
 	exit 1
 }
 
+# loading_throbber() - Loading throbber process for Docker build initialization
+loading_throbber() {
+    pid=$1
+    delay=0.1
+    spinstr='-\|/'
+
+    while kill -0 "$pid" 2>/dev/null
+    do
+        temp=${spinstr#?}
+        state=$(awk '$1 == "Step" { print $2 }' "$TEMP_OUTPUT" | tail -n 1)
+        spinstr=$temp${spinstr%"$temp"}
+        # Getting the last line of the output of the long command
+        if [ "$state" ]; then
+            printf '\r[%c] %s: Initialization of the environment (%s)' "$spinstr" "$PROGNAME" "$state"
+            line_length=$((46 + ${#state}))
+        else
+            printf '\r[%c] %s: Initialization of the environment' "$spinstr" "$PROGNAME"
+        fi
+        sleep $delay
+    done
+}
+
 # docker_build() - Initialize build container
 docker_build() {
+	export BUILDKIT_PROGRESS=plain
+	TEMP_OUTPUT=$(mktemp -u)
+	line_length=46
+
 	if [ -z "$project_build_context" ]; then
-		docker build ${quiet:+-q} $CQFD_EXTRA_BUILD_ARGS -t "$docker_img_name" "$(dirname "$dockerfile")"
+		docker build ${quiet:+-q} $CQFD_EXTRA_BUILD_ARGS -t "$docker_img_name" "$(dirname "$dockerfile")" > "$TEMP_OUTPUT" 2>&1 &
 	else
-		docker build ${quiet:+-q} $CQFD_EXTRA_BUILD_ARGS -t "$docker_img_name" "${project_build_context}" -f "$dockerfile"
+		docker build ${quiet:+-q} $CQFD_EXTRA_BUILD_ARGS -t "$docker_img_name" "${project_build_context}" -f "$dockerfile" > "$TEMP_OUTPUT" 2>&1 &
+	fi
+	container_init_command_pid=$!
+
+	if [ "$quiet" ]; then
+		# If quiet mode is enabled, we don't display the throbber
+		# and we wait for the docker build to finish
+		wait $container_init_command_pid
+		cat "$TEMP_OUTPUT"
+		rm "$TEMP_OUTPUT"
+		return 0
 	fi
+
+	# Start the throbber
+	loading_throbber $container_init_command_pid
+
+	# Wait for the docker build to finish
+	if ! wait $container_init_command_pid; then
+		printf "\r%${line_length}s\r"
+		cat "$TEMP_OUTPUT" 1>&2
+		rm "$TEMP_OUTPUT"
+		die 'Initialization of environment failed'
+	fi
+
+	# Clean up the output file and the console
+	printf "\r%${line_length}s\r"
+	rm "$TEMP_OUTPUT"
 }
 
 # docker_run() - run command in configured container
@@ -465,7 +516,9 @@ while [ $# -gt 0 ]; do
 	"--init")
 		config_load $flavor
 		docker_build
-		exit $?
+		ret=$?
+		[ "$quiet" ] || echo "$PROGNAME: Initialization of environment successful"
+		exit $ret
 		;;
 	"--flavors")
 		config_load