Add mechanism for patching files in containers

This patch adds a way to patch files in a Docker
image built by Kolla. This is very useful for several
reasons, specifically:

- Custom modifications
- The stable branch of some library has a fix but no pip
  package has been released
- Eliminates the need to package your own pip packages
- Eliminates the need to invent your own versioning to prevent
  upstream versioning
- Eliminates the need to manage a pip server
- In other words, it eliminates the need to get a wheel into
  the image and install it manually using any method not
  previously mentioned

It is also highly desirable because, although Kolla can replace
the source for a service with a custom URL for a tarball or its
own Git repo, it cannot do this for dependencies pulled from pip.

I would also like to point out that this is a feature with its own
code path and works only if the user "inserts" a patch into the folder
patches/docker-image/something.patch and creates an analogous series
file for patch source code.

Simply said, this code will never interfere with the upstream build process
since this feature is not intended for use in upstream.
It is rather meant for downstream users who know what they are doing.
Now they just have an option to patch their images.

Everything works on all layers of the Docker image and stores a report
of applied patches which can then be seen in /etc.

This mechanism is similar as debian patch quilt.

Change-Id: I61d0790c5d4d070b7ea9e8c99c0a76ff5d22bf9d

3 files changed, 35 insertions, 1 deletions

diff --git a/kolla/common/config.py b/kolla/common/config.py
index 4a6fd4903..3075052ad 100644
--- a/kolla/common/config.py
+++ b/kolla/common/config.py
@@ -178,6 +178,8 @@ _CLI_OPTS = [
                help='The network mode for Docker build. Example: host'),
     cfg.BoolOpt('cache', default=True,
                 help='Use the container engine cache when building'),
+    cfg.StrOpt('patches-path', default=None,
+               help='The path where patch files to be applied are located'),
     cfg.StrOpt('platform', default=None,
                help=('The platform to use for a cross-compile build. Should '
                      'be set in conjunction with "--base-arch" argument. '
diff --git a/kolla/image/build.py b/kolla/image/build.py
index 88189e2f7..9b6571d36 100644
--- a/kolla/image/build.py
+++ b/kolla/image/build.py
@@ -140,6 +140,7 @@ def run_build():
     kolla.setup_working_dir()
     kolla.find_dockerfiles()
     kolla.create_dockerfiles()
+    kolla.create_patch_files()
     kolla.build_image_list()
     kolla.find_parents()
     kolla.filter_images()
diff --git a/kolla/image/kolla_worker.py b/kolla/image/kolla_worker.py
index 1e3f4d861..798c8eaa7 100644
--- a/kolla/image/kolla_worker.py
+++ b/kolla/image/kolla_worker.py
@@ -141,6 +141,7 @@ class KollaWorker(object):
         self.image_statuses_unbuildable = dict()
         self.image_statuses_allowed_to_fail = dict()
         self.maintainer = conf.maintainer
+        self.patches_path = conf.patches_path
 
         try:
             self.engine_client = engine.getEngineClient(self.conf)
@@ -322,7 +323,8 @@ class KollaWorker(object):
                       'distro_package_manager': self.distro_package_manager,
                       'rpm_setup': self.rpm_setup,
                       'build_date': build_date,
-                      'clean_package_cache': self.clean_package_cache}
+                      'clean_package_cache': self.clean_package_cache,
+                      'patches_path': self.patches_path}
             env = jinja2.Environment(  # nosec: not used to render HTML
                 loader=jinja2.FileSystemLoader(self.working_dir))
             env.filters.update(self._get_filters())
@@ -349,6 +351,35 @@ class KollaWorker(object):
                 f.write(content)
                 LOG.debug("Wrote it to %s", content_path)
 
+    def create_patch_files(self):
+        for path in self.docker_build_paths:
+            image_name = os.path.basename(path)
+            src_patch_folder = os.path.join(self.patches_path, image_name) if \
+                self.patches_path and os.path.isdir(self.patches_path) \
+                else None
+            dest_patch_folder = os.path.join(path, "patches")
+            os.makedirs(dest_patch_folder, exist_ok=True)
+
+            if not src_patch_folder or not os.path.isdir(src_patch_folder):
+                continue
+
+            src_series_path = os.path.join(src_patch_folder, "series")
+            dest_series_path = os.path.join(dest_patch_folder, "series")
+
+            if os.path.isfile(src_series_path):
+                shutil.copyfile(src_series_path, dest_series_path)
+                with open(src_series_path) as f:
+                    patch_files = [line.strip() for line in f
+                                   if not line.startswith("#")]
+            else:
+                patch_files = []
+
+            for patch_file in patch_files:
+                src_patch_file = os.path.join(src_patch_folder, patch_file)
+                dest_patch_file = os.path.join(dest_patch_folder, patch_file)
+                if os.path.isfile(src_patch_file):
+                    shutil.copyfile(src_patch_file, dest_patch_file)
+
     def _merge_overrides(self, overrides):
         tpl_name = os.path.basename(overrides[0])
         with open(overrides[0], 'r') as f: