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
11f65c6c1d