journalctl: add --user-unit= switch

Add --user-unit= to make it possible to query for user logs by the name
of the service.

shell-completion/systemd-bash-completion.sh

@@ -300,7 +300,7 @@ _journalctl() {
                               -h --help -l --local --new-id128 -m --merge --no-pager
                               --no-tail -q --quiet --setup-keys --this-boot --verify
                               --version --list-catalog --update-catalog'
-                       [ARG]='-D --directory -F --field -o --output -u --unit'
+                       [ARG]='-D --directory -F --field -o --output -u --unit --user-unit'
                 [ARGUNKNOWN]='-c --cursor --interval -n --lines -p --priority --since --until
                               --verify-key'
         )
@@ -320,6 +320,9 @@ _journalctl() {
                         --unit|-u)
                                 comps=$(journalctl -F '_SYSTEMD_UNIT')
                         ;;
+                        --user-unit)
+                                comps=$(journalctl -F '_SYSTEMD_USER_UNIT')
+                        ;;
                         *)
                                 return 0
                         ;;

shell-completion/systemd-zsh-completion.zsh

@@ -70,6 +70,7 @@ _ctls()
                 {-c,--cursor=}'[Start showing entries from specified cursor]:cursors:_journal_fields __CURSORS' \
                 {-b,--this-boot}'[Show data only from current boot]' \
                 {-u,--unit=}'[Show data only from the specified unit]:units:_journal_fields _SYSTEMD_UNIT' \
+                '--user-unit[Show data only from the specified user session unit]:units:_journal_fields _SYSTEMD_USER_UNIT' \
                 {-p,--priority=}'[Show only messages within the specified priority range]:priority:_journal_fields PRIORITY' \
                 {-f,--follow}'[Follow journal]' \
                 {-n,--lines=}'[Number of journal entries to show]:integer' \