Add autocomplete based on omelette library

Readme.md

@@ -254,9 +254,44 @@ You can enable `--harmony` option in two ways:
 * Use `#! /usr/bin/env node --harmony` in the sub-commands scripts. Note some os version don’t support this pattern.
 * Use the `--harmony` option when call the command, like `node --harmony examples/pm publish`. The `--harmony` option will be preserved when spawning sub-command process.
 
+## Autocomplete
+
+commander has autocomplete capability builtin, and you can enable it by the following steps:
+
+1. Declare the candidate values for each option and arg. The candidate value can be an array or a function that receives typedArgs (an array of already typed command line string split by empty space) and returns an array of candidates.
+
+```js
+program
+  .arguments('<a> <b>')
+  .option('--verbose', 'verbose')
+  .option('-n, --name <name>', 'specify name')
+  .option('--description <desc>', 'specify description')
+  .complete({
+    options: {
+      '--name': function(typedArgs) { return ['kate', 'jim']; },
+      '--description': ['desc1', 'desc2']
+    },
+    arguments: {
+      a: function(typedArgs) { return ['a-1', 'a-2']; },
+      b: ['b-1', 'b-2']
+    }
+  });
+```
+
+2. Ask your command line user to enable autocompletion for current session by executing the following command.
+For persistent support, we can recommend adding the command to their shell initialization file such as .bashrc or .zshrc etc.
+
+```
+# for zsh or bash
+eval "$(<cli-program-name> --completion)"
+
+# for fish shell
+<cli-program-name> --completion-fish | source
+```
+
 ## Automated --help
 
- The help information is auto-generated based on the information commander already knows about your program, so the following `--help` info is for free:
+The help information is auto-generated based on the information commander already knows about your program, so the following `--help` info is for free:
 
 ```  
 $ ./examples/pizza --help

Readme_zh-CN.md

@@ -181,6 +181,40 @@ Commander 将会尝试在入口脚本（例如 `./examples/pm`）的目录中搜
 * 在子命令脚本中加上 `#!/usr/bin/env node --harmony`。注意一些系统版本不支持此模式。
 * 在指令调用时加上 `--harmony` 参数，例如 `node --harmony examples/pm publish`。`--harmony` 选项在开启子进程时会被保留。
 
+## 自动补全
+
+commander 已自带命令行自动补全功能。您可以按照以下步骤启用它：
+
+1. 声明对应每个选项和参数的候选值。候选值可以是一个数组或者是一个 接受当前已经输入值的数组然后返回一个候选数组的function。
+
+```js
+program
+  .arguments('<a> <b>')
+  .option('--verbose', 'verbose')
+  .option('-n, --name <name>', 'specify name')
+  .option('--description <desc>', 'specify description')
+  .complete({
+    options: {
+      '--name': function(typedArgs) { return ['kate', 'jim']; },
+      '--description': ['desc1', 'desc2']
+    },
+    arguments: {
+      a: function(typedArgs) { return ['a-1', 'a-2']; },
+      b: ['b-1', 'b-2']
+    }
+  });
+```
+
+2. 邀请你的命令行用户开启自动补全功能。他们可以直接在shell执行以下指令，或是把其加入到个人shell对应的.bashrc或.zshrc等文件中，就可以获得长期的自动补全支持。
+
+```
+# for zsh or bash
+eval "$(<cli-program-name> --completion)"
+
+# for fish shell
+<cli-program-name> --completion-fish | source
+```
+
 ## 自动化帮助信息 --help
 
  帮助信息是 commander 基于你的程序自动生成的，下面是 `--help` 生成的帮助信息：

examples/autocomplete

@@ -0,0 +1,30 @@
+#!/usr/bin/env node
+
+/**
+ * To simulate real use cases please set the example path into PATH variable
+ * export PATH=".":$PATH
+ *
+ * Then please execute the following line to enable completion for your shell
+ * eval "$(autocomplete --completion)"
+ *
+ * And then you can try use tab completion after auto-complete command
+ */
+
+var program = require('..');
+
+program
+  .arguments('<a> <b>')
+  .option('--verbose', 'verbose')
+  .option('-n, --name <name>', 'specify name')
+  .option('--description <desc>', 'specify description')
+  .complete({
+    options: {
+      '--name': function() { return ['kate', 'jim']; },
+      '--description': ['desc1', 'desc2']
+    },
+    arguments: {
+      a: function() { return ['a-1', 'a-2']; },
+      b: ['b-1', 'b-2']
+    }
+  })
+  .parse(process.argv);

examples/autocomplete-sub

@@ -0,0 +1,46 @@
+#!/usr/bin/env node
+
+/**
+ * To simulate real use cases please set the example path into PATH variable
+ * export PATH=".":$PATH
+ *
+ * Then please execute the following line to enable completion for your shell
+ * eval "$(autocomplete-sub --completion)"
+ */
+
+var program = require('..');
+
+program
+  .command('sub1 <arg1> <arg2>')
+  .description('sub command 1')
+  .option('--verbose', 'verbose')
+  .option('-n, --name <name>', 'specify name')
+  .option('--description <desc>', 'specify description')
+  .complete({
+    options: {
+      '--name': function() { return ['kate', 'jim']; },
+      '--description': ['d1', 'd2']
+    },
+    arguments: {
+      arg1: function() { return ['a-1', 'a-2', 'a-3']; },
+      arg2: ['b-1', 'b-2']
+    }
+  });
+
+program
+  .command('sub2 <arg1>')
+  .description('sub command 2')
+  .option('--verbose', 'verbose')
+  .option('-n, --name <name>', 'specify name')
+  .option('--description <desc>', 'specify description')
+  .complete({
+    options: {
+      '--name': function() { return ['lucy', 'linda']; },
+      '--description': ['db1', 'db2']
+    },
+    arguments: {
+      arg1: function() { return ['a-11', 'a-12']; },
+    }
+  });
+
+program.parse(process.argv);