feat(logcli): add completion plugin (#14158)

plugins/logcli/logcli.plugin.zsh

@@ -0,0 +1,18 @@
+# Autocompletion for Grafana Loki's CLI (logcli).
+if (( ! $+commands[logcli] )); then
+  return
+fi
+
+# If the completion file doesn't exist yet, we need to autoload it and
+# bind it to `logcli`. Otherwise, compinit will have already done that.
+if [[ ! -f "$ZSH_CACHE_DIR/completions/_logcli" ]]; then
+  typeset -g -A _comps
+  autoload -Uz _logcli
+  _comps[logcli]=_logcli
+fi
+
+zmodload -F zsh/files b:zf_mv
+() {
+  local TMPPREFIX="$ZSH_CACHE_DIR/completions/._logcli"
+  zf_mv -f -- =( logcli --completion-script-zsh ) "$ZSH_CACHE_DIR/completions/_logcli"
+} &|