implements patch support for repos

With this commit its now possible to patch 3rd party repos before bitbake is started.

Example:

This is our repo:
  .
  ├── kas.yml
  ├── first-patch.patch
  └── quilt-patches
      ├── second-patch.patch
      ├── third-patch.patch
      └── series

Content of kas.yml:
  header:
    version: 8

  repos:
    my:
    third-party:
      url: "git://example.com/third-party.git"
      refspec: "35adf4...34"
      patches:
        01-first:
          repo: my
          path: "first-patch.patch"
        02-second:
          repo: my
          path: "quilt-patches"

Currently only 'git' repositories can be patched.

Signed-off-by: Claudius Heine <ch@denx.de>

kas/libkas.py

@@ -184,6 +184,27 @@ def repos_fetch(config, repos):
             sys.exit(task.result())
 
 
+def repos_apply_patches(config, repos):
+    """
+        Applies the patches to the repositories.
+    """
+    tasks = []
+    for repo in repos:
+        if not hasattr(asyncio, 'ensure_future'):
+            # pylint: disable=no-member,deprecated-method
+            task = asyncio.async(repo.apply_patches_async(config))
+        else:
+            task = asyncio.ensure_future(repo.apply_patches_async(config))
+        tasks.append(task)
+
+    loop = asyncio.get_event_loop()
+    loop.run_until_complete(asyncio.wait(tasks))
+
+    for task in tasks:
+        if task.result():
+            sys.exit(task.result())
+
+
 def get_build_environ(config, build_dir):
     """
         Create the build environment variables.