co'ifying https://github.com/dlasky/grunt-git-tag-parse/blob/769275fca5b0b25d0902b87d818e3b75d32ef632/tasks/git_tag_parse.js

_1.js

/*
 * grunt-git-tag-parse
 * https://github.com/dlasky/grunt-git-tag-parse
 *
 * Copyright (c) 2014 Dan Lasky
 * Licensed under the MIT license.
 */

'use strict';

var when = require('when'),
  co = require('co');

module.exports = function(grunt) {

  
  function spawn(options) {
    var def = when.defer();
    grunt.util.spawn(options, function(err, result, code) {
      if (err) { def.reject(err); }
      if (result) { def.resolve(String(result)); }
    });
    return def.promise;
  }

  grunt.registerMultiTask('git_tag_parse', 'write the current git tag to a variable', function() {

    var options = this.options({
      number: 6,
      revision: "HEAD",
      property: "meta.revision"
    }),
    done = this.async();
    
    function writeResult(data) {
      var dirty = data[0].split("\n"),
        tag = data[1],
        rev = data[2],
        output = "";

      dirty = dirty.filter(function(item) {
        var f = item.slice(0,2);
        return f === "??" || f === " M";
      });

      if (tag !== "no tag") {
        output += tag;
      } else {
        output += rev;
      }

      if (dirty.length) {
        output += "(dirty)";
      }

      grunt.log.ok(output);
      grunt.config.set(options.property, output);
      return output
    }

    co(function * () {

    var list = yield when.all([
        spawn({
          cmd:"git",
          args: ["status","--porcelain"]
        }),
        spawn({
          cmd:"git",
          args: ["describe", "--exact-match", options.revision]
        }).else("no tag"),
        spawn({
          cmd:"git",
          args: ["rev-parse", "--verify", "--short=" + options.number, options.revision]
        })
      ]);
    
    writeResult(list);
    
    }) (done);

  });
};

_2.js

/*
 * grunt-git-tag-parse
 * https://github.com/dlasky/grunt-git-tag-parse
 *
 * Copyright (c) 2014 Dan Lasky
 * Licensed under the MIT license.
 */

'use strict';

var when = require('when'),
  co = require('co');

module.exports = function(grunt) {

  function spawn(options) {
    var def = when.defer();
    grunt.util.spawn(options, function(err, result, code) {
      if (err) { def.reject(err); }
      if (result) { def.resolve(String(result)); }
    });
    return def.promise;
  }

  grunt.registerMultiTask('git_tag_parse', 'write the current git tag to a variable', function() {

    var options = this.options({
      number: 6,
      revision: "HEAD",
      property: "meta.revision"
    }),
    done = this.async();
    
    function writeResult(input, tag, rev) {
      var dirty = input.split("\n"),
        output = "";

      dirty = dirty.filter(function(item) {
        var f = item.slice(0,2);
        return f === "??" || f === " M";
      });

      if (tag !== "no tag") {
        output += tag;
      } else {
        output += rev;
      }

      if (dirty.length) {
        output += "(dirty)";
      }

      grunt.log.ok(output);
      grunt.config.set(options.property, output);
      return output
    }

    co(function * () {
      
    var input = spawn({
        cmd:"git",
        args: ["status","--porcelain"]
      }),
      tag = spawn({
        cmd:"git",
        args: ["describe", "--exact-match", options.revision]
      }).else("no tag"),
      rev = spawn({
        cmd:"git",
        args: ["rev-parse", "--verify", "--short=" + options.number, options.revision]
      });
    
    writeResult(yield input,  yield tag, yield rev);
    
    }) (done);

  });
};

_3.js

/*
 * grunt-git-tag-parse
 * https://github.com/dlasky/grunt-git-tag-parse
 *
 * Copyright (c) 2014 Dan Lasky
 * Licensed under the MIT license.
 */

'use strict';

var when = require('when'),
  co = require('co'),
  nodefn = require('when/node');

module.exports = function(grunt) {

  var spawn = nodefn.lift(grunt.util.spawn);
  
  grunt.registerMultiTask('git_tag_parse', 'write the current git tag to a variable', function() {

    var options = this.options({
      number: 6,
      revision: "HEAD",
      property: "meta.revision"
    }),
    done = this.async();
    
    function writeResult(input, tag, rev) {
      var dirty = input.split("\n"),
        output = "";

      dirty = dirty.filter(function(item) {
        var f = item.slice(0,2);
        return f === "??" || f === " M";
      });

      if (tag !== "no tag") {
        output += tag;
      } else {
        output += rev;
      }

      if (dirty.length) {
        output += "(dirty)";
      }

      grunt.log.ok(output);
      grunt.config.set(options.property, output);
      return output
    }

    co(function * () {
      
    var input = spawn({
        cmd:"git",
        args: ["status","--porcelain"]
      }),
      tag = spawn({
        cmd:"git",
        args: ["describe", "--exact-match", options.revision]
      }).else("no tag"),
      rev = spawn({
        cmd:"git",
        args: ["rev-parse", "--verify", "--short=" + options.number, options.revision]
      });
    
    writeResult(yield input,  yield tag, yield rev);
    
    }) (done);

  });
};

original.js

/*
 * grunt-git-tag-parse
 * https://github.com/dlasky/grunt-git-tag-parse
 *
 * Copyright (c) 2014 Dan Lasky
 * Licensed under the MIT license.
 */

'use strict';

var when = require('when');

module.exports = function(grunt) {

  function spawn(options) {
    var def = when.defer();
    grunt.util.spawn(options, function(err, result, code) {
      if (err) { def.reject(err); }
      if (result) { def.resolve(String(result)); }
    });
    return def.promise;
  }

  grunt.registerMultiTask('git_tag_parse', 'write the current git tag to a variable', function() {

    var options = this.options({
      number: 6,
      revision: "HEAD",
      property: "meta.revision"
    }),
    done = this.async();

    function writeResult(data) {
      var def = when.defer(),
        dirty = data[0].split("\n"),
        tag = data[1],
        rev = data[2],
        output = "";

      dirty = dirty.filter(function(item) {
        var f = item.slice(0,2);
        return f === "??" || f === " M";
      });

      if (tag !== "no tag") {
        output += tag;
      } else {
        output += rev;
      }

      if (dirty.length) {
        output += "(dirty)";
      }

      grunt.log.ok(output);
      grunt.config.set(options.property, output);
      def.resolve(output);
      return def.promise;
    }

    when.all([
      spawn({
        cmd:"git",
        args: ["status","--porcelain"]
      }),
      spawn({
        cmd:"git",
        args: ["describe", "--exact-match", options.revision]
      }).else("no tag"),
      spawn({
        cmd:"git",
        args: ["rev-parse", "--verify", "--short=" + options.number, options.revision]
      })
    ])
    .then(writeResult)
    .done(done);

  });
};