pack.sh: refuse to run if there are uncommited assets

src/build/pack.sh

@@ -15,6 +15,15 @@
 
 set -e
 
+function check_uncommitted_assets() {
+    ( cd assets; [ $(git status --porcelain . | wc -l) -gt 0 ] )
+}
+
+if check_uncommitted_assets; then
+    echo "Please make sure there are no uncommited files in the 'asset' directory before packing"
+    exit 1
+fi
+
 if [ "$1" == "-b" ]; then
     cargo build --release --target=x86_64-unknown-linux-gnu --no-default-features --features release_linux
     cargo build --release --target=x86_64-pc-windows-gnu --no-default-features --features release_windows