A lot of fixes (see description)

- fix indentation (I used a broken vim config)
- add a -d (dry run) option
- add guarding double quotes at a few places
- use `python3` if no `python` executable exists
- explicitly use bash (instead of posix sh) where it is required

init.sh

@@ -1,15 +1,30 @@
 #!/usr/bin/env sh
+
+CUSTOM_PYTHON=
+
+if ! which python > /dev/null; then
+	if which python3 > /dev/null; then
+		echo ">>> python not found, using python3 instead"
+		CUSTOM_PYTHON=python3
+	else
+		echo ">>> No python executable found, please install python or python3"
+		exit 1
+	fi
+fi
+
 if [ -e yt-dlc/ ]; then
-    echo ">>> youtube-dlc already downloaded, delete and redownload? [y/N]"
-    read RES
-    [ "$RES" = "y" ] || [ "$RES" = "Y" ] && rm -rf yt-dlc/
+	printf ">>> youtube-dlc already downloaded, delete and redownload? [y/N]: "
+	read RES
+	[ "$RES" = "y" ] || [ "$RES" = "Y" ] && rm -rf yt-dlc/
 fi
 if [ ! -e yt-dlc/ ]; then
-    echo ">>> Cloning youtube-dlc repo" &&
-    git clone --depth 1 --branch "2020.11.11-3" "https://github.com/blackjack4494/yt-dlc.git"
-    echo ">>> Applying patches"
-    # Allows for downloading English content from the German website
-    patch -p0 < fix-southpark-de-en.diff
+	echo ">>> Cloning youtube-dlc repo" &&
+	git clone --depth 1 --branch "2020.11.11-3" "https://github.com/blackjack4494/yt-dlc.git"
+	echo ">>> Applying patches"
+	# Allows for downloading English content from the German website
+	patch -p0 < fix-southpark-de-en.diff
 fi
 echo ">>> Building youtube-dlc"
 make -C yt-dlc/ youtube-dlc
+[ -n "$CUSTOM_PYTHON" ] &&
+	sed -i "1c\\#!/usr/bin/env $CUSTOM_PYTHON" yt-dlc/youtube-dlc