numerous updates

update

@@ -48,6 +48,16 @@ if [[ -z "$UPDATE_REEXECED" ]]; then
     exec ~/.local/bin/update
 fi
 
+# An upgrade that runs out of disk space part way through can leave the system
+# half-upgraded. Set UPDATE_FORCE=1 to skip this check.
+MIN_FREE_GIB=10
+FREE_KIB="$(df -k --output=avail / | tail -n 1 | tr -d ' ')"
+if [[ -z "$UPDATE_FORCE" && "$FREE_KIB" =~ ^[0-9]+$ ]] && (( FREE_KIB < MIN_FREE_GIB * 1024 * 1024 )); then
+    echo "Only $(( FREE_KIB / 1024 / 1024 )) GiB free on /; updating needs at least $MIN_FREE_GIB GiB."
+    echo "Free up space (sudo paccache -rk1 clears old cached packages), or run: UPDATE_FORCE=1 update"
+    exit 1
+fi
+
 # Ask for the password once, then keep sudo's cached credentials fresh until
 # update exits, so long-running hooks don't stop for a password again.
 sudo -v || exit 1