bash-completion/journalctl: list user units when --user is already specified (#35799)

Also, escape the current input before matching listed user units.

Fixes #35794.

shell-completion/bash/journalctl

@@ -94,7 +94,11 @@ _journalctl() {
                 compopt -o nosort
                 ;;
             --unit|-u)
-                comps=$(journalctl -F '_SYSTEMD_UNIT' 2>/dev/null)
+                if __contains_word "--user" ${COMP_WORDS[*]}; then
+                     comps=$(journalctl -F '_SYSTEMD_USER_UNIT' 2>/dev/null)
+                else
+                     comps=$(journalctl -F '_SYSTEMD_UNIT' 2>/dev/null)
+                fi
                 # Similarly to systemctl, we need to distinguish between
                 # escaped and unescaped names in order to be able to correctly
                 # complete them. In this particular case, if the name we're
@@ -109,6 +113,10 @@ _journalctl() {
                 ;;
             --user-unit)
                 comps=$(journalctl -F '_SYSTEMD_USER_UNIT' 2>/dev/null)
+                if ! [[ $cur =~ '\\' ]]; then
+                    cur="$(printf '%q' $cur)"
+                fi
+                compopt -o filenames
                 ;;
             --identifier|-t|--exclude-identifier|-T)
                 comps=$(journalctl -F 'SYSLOG_IDENTIFIER' 2>/dev/null)