Implement "rm" subcommand

Makefile

@@ -1,5 +1,7 @@
 test:
 	bash_unit ./tests/test_*.sh
+runtests:
+	ls -1 zk tests/* | entr -c bash_unit ./tests/test_*.sh
 install:
 	test -d ~/.local/bin/ || mkdir -p ~/.local/bin/
 	cp zk ~/.local/bin/zk

zk

@@ -63,6 +63,20 @@ _zk_edit() {
 	fi
 }
 
+_zk_rm() {
+	if test -z "$1"; then
+		echo "zk rm: no zettel id given" 1>&2
+		exit 1
+	fi
+
+	if ! find "$ZKDIR" -name "$1" | grep .; then
+		echo "zk rm: zettel "$1" not found" 1>&2
+		exit 2
+	fi
+
+	rm "$ZKDIR/$1"
+}
+
 main() {
 	check_zkdir