feat(buf): add completion plugin

plugins/buf/README.md

@@ -0,0 +1,9 @@
+# Buf plugin
+
+This plugin adds completion for [Buf CLI](https://github.com/bufbuild/buf), a tool working with Protocol Buffers.
+
+To use it, add `buf` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... buf)
+```

plugins/buf/buf.plugin.zsh

@@ -0,0 +1,14 @@
+# Autocompletion for the Buf CLI (buf).
+if (( !$+commands[buf] )); then
+  return
+fi
+# If the completion file doesn't exist yet, we need to autoload it and
+# bind it to `buf`. Otherwise, compinit will have already done that.
+if [[ ! -f "$ZSH_CACHE_DIR/completions/_buf" ]]; then
+  typeset -g -A _comps
+  autoload -Uz _buf
+  _comps[buf]=_buf
+fi
+
+# Generate and load buf completion
+buf completion zsh >! "$ZSH_CACHE_DIR/completions/_buf" &|