Add upgrade-rootfs.sh script and overlays Makefile target

Makefile

@@ -32,9 +32,15 @@ endif
 .PHONY: build
 build: $(OUTPUT_FILE)
 
+EXTRACT_DIR := tmp/extracted
+
 .PHONY: extract
 extract: firmware/$(FIRMWARE_FILE) tools
-	./scripts/extract_squashfs.sh $< tmp/extracted
+	./scripts/extract_squashfs.sh $< $(EXTRACT_DIR)
+
+.PHONY: overlays
+overlays:
+	@echo $(OVERLAYS)
 
 .PHONY: profiles
 profiles:

scripts/dev/upgrade-rootfs.sh

@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+if [[ $# -lt 2 ]]; then
+  echo "usage: $0 <user@ip> <profile> [command]"
+  exit 1
+fi
+
+SSH_HOST="$1"
+PROFILE="$2"
+shift 2
+
+PASSWORD="${PASSWORD:-snapmaker}"
+SSH_OPTS="-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null"
+
+overlays_list() {
+  make -s overlays PROFILE="$1"
+}
+
+tar_overlays_root() {
+  for overlay; do
+    [[ -d "$overlay/root" ]] && echo "-C $(realpath "$overlay/root") ."
+  done
+}
+
+# Use `tar` instead of `scp` as being significantly faster when there are many small files.
+
+echo ">> Uploading rootfs overlays..."
+tar -cf - $(tar_overlays_root $(overlays_list "$PROFILE")) |
+  sshpass -p "$PASSWORD" ssh $SSH_OPTS "$SSH_HOST" tar -C / -xf -
+
+if [[ $# -gt 0 ]]; then
+  echo ">> Running command: $*"
+  sshpass -p "$PASSWORD" ssh $SSH_OPTS "$SSH_HOST" "$@"
+fi
+
+echo ">> Done."