Add netlify-git backend

src/backends/github/implementation.js

@@ -1,7 +1,10 @@
+import semaphore from 'semaphore';
 import {createEntry} from '../../valueObjects/Entry';
 import AuthenticationPage from './AuthenticationPage';
 import API from './API';
 
+const MAX_CONCURRENT_DOWNLOADS = 10;
+
 export default class GitHub {
   constructor(config) {
     this.config = config;
@@ -29,13 +32,19 @@ export default class GitHub {
   }
 
   entries(collection) {
-    return this.api.listFiles(collection.get('folder')).then((files) => (
-      Promise.all(files.map((file) => (
-        this.api.readFile(file.path, file.sha).then((data) => {
-          return createEntry(file.path, file.path.split('/').pop().replace(/\.[^\.]+$/, ''), data);
-        })
-      )))
-    )).then((entries) => ({
+    return this.api.listFiles(collection.get('folder')).then((files) => {
+      const sem = semaphore(MAX_CONCURRENT_DOWNLOADS);
+      const promises = [];
+      files.map((file) => {
+        sem.take(() => {
+          promises.push(this.api.readFile(file.path, file.sha).then((data) => {
+            sem.leave();
+            return createEntry(file.path, file.path.split('/').pop().replace(/\.[^\.]+$/, ''), data);
+          }));
+        });
+      });
+      return Promise.all(promises);
+    }).then((entries) => ({
       pagination: {},
       entries
     }));