Update zet script

scripts/scripts/zet

@@ -1,13 +1,32 @@
 #!/bin/sh
 
+set -e
+
 # Creates a new `zet` inside the public `Zettlekasten` directory.
 
-dirname="$(isosec)"
-mkdir "$ZETDIR/$dirname"
-dir="$ZETDIR/$dirname"
+_cmd_exists() {
+  command -v "$@" >/dev/null 2>&1
+}
+
+# Early out if the directory is not found.
+! test -d "$ZETDIR" && echo "Can't find ${ZETDIR:-'Not Found in ENV'}" && exit 1
+
+# Early out if `isosec` is not found.
+! _cmd_exists isosec && echo "isosec not found." && exit
+
+# Create a new directory for this note.
+dir="$ZETDIR/$(isosec)"
+mkdir "$dir"
+
+# Create the readme file with the title (if supplied)
 readme="$dir/README.md"
 title="$*"
 printf "# %s\n\n" "${title}" > "${readme}"
+
+# Bail if the readme was not created.
+! test -r "$readme" && echo "README was not created properly." && exit 1
+
+# Auto commit the new note.
 message="${title:-"Autocommit message"}"
 cd "$dir"
 git pull -q
@@ -15,4 +34,6 @@ git add -A "$dir"
 git commit -m "$message"
 git push
 cd -
-vi "${readme}"
+
+# Open the note.
+exec vi "${readme}"