feat!: use XDG_DATA_HOME as AGENDA_DIR fallback

I first decided against this, but the old `~/.app-trash` is no more
fitting than the XDG_DATA_HOME location.

The xdg-user-dir DOCUMENTS fallback is too presumptuous and removing it
makes things even simpler.

agenda

@@ -57,11 +57,7 @@ __main() {
 	esac
 
 	if [ -z "$AGENDA_DIR" ]; then
-		if type xdg-user-dir >/dev/null 2>&1; then
-			AGENDA_DIR="$(xdg-user-dir DOCUMENTS)/agenda"
-		else
-			AGENDA_DIR="$HOME/.agenda"
-		fi
+		AGENDA_DIR="${XDG_DATA_HOME:-"$HOME/.local/share"}/agenda"
 	fi
 
 	# Subcommand

agenda.1

@@ -107,9 +107,7 @@ The editor process has access to certain environment variables.
 \fBAGENDA_DIR\fP
 .RS 4
 The home of all agenda note files read and written by agenda. If this is empty
-agenda will attempt to find the \fIxdg-user-dir DOCUMENTS\fP directory if
-\fBxdg-user-dir(1)\fP is found in \fBPATH\fP. Otherwise `$HOME/.agenda` will be
-used.
+`${XDG_DATA_HOME:-"$HOME/.local/share"}/agenda` will be used.
 .PP
 .RE
 \#
@@ -192,11 +190,6 @@ The last agenda file. Can be empty if no previous agenda note exists.
 .RE
 \#=============================================================================
 .SH "SEE ALSO"
-\fBxdg-user-dir(1)\fP
-.RS 4
-Used to find the default \fBAGENDA_DIR\fP.
-.PP
-.RE
 \fBdate(1)\fP
 .RS 4
 Your installation of date determines which date formats for the \fI<date>\fP

completion.bash

@@ -5,11 +5,7 @@
 # TODO: Maybe its easier to add an api to the agenda script to query for the
 #       available -t option values?
 if [ -z "$AGENDA_DIR" ]; then
-	if type xdg-user-dir >/dev/null 2>&1; then
-		AGENDA_DIR="$(xdg-user-dir DOCUMENTS)/agenda"
-	else
-		AGENDA_DIR="$HOME/.agenda"
-	fi
+	AGENDA_DIR="${XDG_DATA_HOME:-"$HOME/.local/share"}/agenda"
 fi
 
 AGENDA_COMP_DATE_MOD=("next" "last")