Fix locale handling, menu re-entry and empty-checkupdates logging

- The runner now forces LC_ALL=C itself instead of relying on the unit's
  Environment=. pacman failures are classified by matching its output, so a
  run started by hand on a German system was misclassifying every failure.
- 'Update now' in the menu exec'd the runner, which terminated the menu.
- Log a distinct message when checkupdates is unavailable, instead of
  claiming zero pending packages before a full upgrade.

src/cachy-auto-update

@@ -170,7 +170,9 @@ cau_do_status() {
 
 cau_do_run() {
 	cau_need_root
-	exec "$CAU_LIBEXECDIR/cachy-auto-update-run" "$@"
+	# Not exec'd: this is also called from the menu, which has to survive the
+	# run and redraw afterwards.
+	"$CAU_LIBEXECDIR/cachy-auto-update-run" "$@"
 }
 
 cau_do_log() {

src/cachy-auto-update-run

@@ -40,6 +40,13 @@ if [[ $EUID -ne 0 ]]; then
 	exit 2
 fi
 
+# Force a neutral locale here rather than relying on the unit's Environment=,
+# so a run started by hand behaves exactly like one started by the timer.
+# pacman failures are classified by matching its output, and on a German system
+# that output is German. Text aimed at a person does not come through here - a
+# notification is rendered in the recipient's own locale by cau_msg_in.
+export LC_ALL=C LANGUAGE=
+
 # Re-exec under an inhibitor so a suspend or shutdown cannot land in the middle
 # of a pacman transaction and leave the database half-written. Done before
 # anything else so the whole pass is covered, including the lock.

src/lib/pkg_pacman.sh

@@ -76,9 +76,16 @@ cau_pacman_update() {
 		return 0
 	fi
 
-	CAU_PACMAN_COUNT="$(grep -c . <<< "$CAU_PACMAN_PENDING")"
-	[[ $CAU_PACMAN_COUNT =~ ^[0-9]+$ ]] || CAU_PACMAN_COUNT=0
-	cau_info "Updating $CAU_PACMAN_COUNT repository package(s)"
+	if [[ -n $CAU_PACMAN_PENDING ]]; then
+		CAU_PACMAN_COUNT="$(grep -c . <<< "$CAU_PACMAN_PENDING")"
+		[[ $CAU_PACMAN_COUNT =~ ^[0-9]+$ ]] || CAU_PACMAN_COUNT=0
+		cau_info "Updating $CAU_PACMAN_COUNT repository package(s)"
+	else
+		# checkupdates is unavailable, so the list is unknown and pacman is
+		# asked to work it out itself.
+		CAU_PACMAN_COUNT=0
+		cau_info "Running a full system upgrade (pending list unavailable)"
+	fi
 
 	mapfile -t flags < <(cau_pacman_flags)
 	log="$(mktemp)" || return 1