--env: use CLI::Parser.

Library/Homebrew/cmd/--env.rb

@@ -1,36 +1,46 @@
-#:  * `--env` [`--shell=`(<shell>|`auto`)|`--plain`]:
-#:    Show a summary of the Homebrew build environment as a plain list.
-#:
-#:    Pass `--shell=`<shell> to generate a list of environment variables for the
-#:    specified shell, or `--shell=auto` to detect the current shell.
-#:
-#:    If the command's output is sent through a pipe and no shell is specified,
-#:    the list is formatted for export to `bash`(1) unless `--plain` is passed.
-
 require "extend/ENV"
 require "build_environment"
 require "utils/shell"
+require "cli_parser"
 
 module Homebrew
   module_function
 
+  def __env_args
+    Homebrew::CLI::Parser.new do
+      usage_banner <<~EOS
+        `--env` [<options>]
+
+        Show a summary of the Homebrew build environment as a plain list.
+
+        If the command's output is sent through a pipe and no shell is specified,
+        the list is formatted for export to `bash`(1) unless `--plain` is passed.
+      EOS
+      flag "--shell=",
+        description: "Generate a list of environment variables for the specified shell, " \
+                     "or `--shell=auto` to detect the current shell."
+      switch "--plain",
+        description: "Plain output even when piped."
+    end
+  end
+
   def __env
+    __env_args.parse
+
     ENV.activate_extensions!
     ENV.deps = ARGV.formulae if superenv?
     ENV.setup_build_environment
     ENV.universal_binary if ARGV.build_universal?
 
-    shell_value = ARGV.value("shell")
-
-    if ARGV.include?("--plain")
-      shell = nil
-    elsif shell_value.nil?
+    shell = if args.plain?
+      nil
+    elsif args.shell.nil?
       # legacy behavior
-      shell = :bash unless $stdout.tty?
-    elsif shell_value == "auto"
-      shell = Utils::Shell.parent || Utils::Shell.preferred
-    elsif shell_value
-      shell = Utils::Shell.from_path(shell_value)
+      :bash unless $stdout.tty?
+    elsif args.shell == "auto"
+      Utils::Shell.parent || Utils::Shell.preferred
+    elsif args.shell
+      Utils::Shell.from_path(args.shell)
     end
 
     env_keys = build_env_keys(ENV)