zsh:alias: Turn tmsu into a smarter function

Instead of simply pointing the database to XDG_DATA_HOME, write a
wrapper function that searches for `.tmsu/db` in all parent directories
and fallbacks to XDG_DATA_HOME if not found.

Also create XDG_DATA_HOME/tmsu if necessary.

.config/zsh/zshrc.d/30-alias.zsh

@@ -44,7 +44,6 @@ fi
 
 # XDG Base Directory Specification
 	add_flags tmux -f "${XDG_CONFIG_HOME:-$HOME/.config}/tmux/tmux.conf"
-	add_flags tmsu -D "${XDG_DATA_HOME:-$HOME/.local/share}/tmsu/db"
 	add_flags yarn --use-yarnrc "${XDG_CONFIG_HOME:-$HOME/.config}"/yarn/config
 	add_flags bash --rcfile "${XDG_CONFIG_HOME:-$HOME/.config}"/bash/bashrc
 	add_flags mbsync -c "$XDG_CONFIG_HOME"/isync/mbsyncrc

.config/zsh/zshrc.d/40-functions.zsh

@@ -579,3 +579,28 @@ finddup() {
 	| uniq -w32 --all-repeated=separate \
 	| awk '{print $2}'
 }
+
+# Wrapper around tmsu that searches for .tmsu/db in all parent directories and
+# fallbacks to XDG_DATA_HOME if not found.
+tag() {
+	if (( ! $+commands[tmsu] )); then
+		printf >&2 "tmsu not installed.\n"
+		return 1
+	fi
+
+	local db dir="$PWD" std=".tmsu/db"
+
+	# Go up directories until root to find .tmsu/db
+	until [[ -e $dir/$std || $dir = / ]]; do
+		dir="${dir:h}"
+	done
+	db="$dir/$std"
+
+	# Fallback to XDG_DATA if .tmsu/db was not found in one of the parent dirs.
+	if [[ ! -e $db ]]; then
+		db="${XDG_DATA_HOME:-$HOME/.local/share}"/tmsu/db
+		mkdir -p "${db:h}"
+	fi
+
+	env TMSU_DB="$db" tmsu "$@"
+}