[WIP] add github plugin.

Signed-off-by: Eric Wang <skygragon@gmail.com>

Author: skygragon

github.js

@@ -0,0 +1,85 @@
+var path = require('path');
+var url = require('url');
+
+var GitHubApi = require('github');
+
+var h = require('../helper');
+var log = require('../log');
+var Plugin = require('../plugin');
+
+// [prerequisite]
+//
+// 1. create a new access token on your github repo setting. (TBD)
+//
+// [config]
+//
+// "PLUGINS": {
+//   "github": {
+//     "repo": "https://github.com/<your_name>/<your_repo>/<folder_you_like>",
+//     "token": "<token created above>"
+//   }
+// }
+var plugin = new Plugin(100, 'github', '2017.08.09',
+    'Plugin to commit accepted code to your own github repo.');
+
+var github = new GitHubApi({
+  host: 'api.github.com'
+});
+
+var ctx = {};
+
+plugin.submitProblem = function(problem, cb) {
+  var parts = url.parse(this.config.repo).pathname.split('/');
+  var filename = path.basename(problem.file);
+  parts.push(filename);
+
+  if (parts[0] === '') parts.shift();
+  ctx.owner = parts.shift();
+  ctx.repo = parts.shift();
+  ctx.path = parts.join('/');
+
+  github.authenticate({type: 'token', token: this.config.token});
+  plugin.next.submitProblem(problem, function(_e, results) {
+    if (_e || !results[0].ok) return cb(_e, results);
+
+    log.debug('running github.getContent: ' + filename);
+    github.repos.getContent(ctx, function(e, res) {
+      if (e && e.code !== 404) {
+        log.error('[github] failed: ' + e.message);
+        return cb(_e, results);
+      }
+
+      ctx.message = 'update ' + filename;
+      ctx.content = new Buffer(h.getFileData(problem.file)).toString('base64');
+
+      var onFileDone = function(e, res) {
+        if (e) {
+          log.error('[github] failed: ' + e.message);
+          return cb(_e, results);
+        }
+
+        log.debug(res.meta.status);
+        log.debug('updated current file version = ' + res.data.content.sha);
+        log.debug('updated current commit = ' + res.data.commit.sha);
+
+        log.info('[github] successfully committed to ' + plugin.config.repo);
+        return cb(_e, results);
+      };
+
+      if (e) {
+        log.debug('no previous file version found');
+
+        log.debug('running github.createFile');
+        github.repos.createFile(ctx, onFileDone);
+      } else {
+        ctx.sha = res.data.sha;
+        log.debug('found previous file version = ' + ctx.sha);
+
+        log.debug('running github.updateFile');
+        github.repos.updateFile(ctx, onFileDone);
+      }
+    });
+  });
+};
+
+module.exports = plugin;