[mythtv] FFmpeg plans

[Peter Bennett]

Thank you Brian Murrell for the helpful information.

This is my take on the whole submodule/subtree/subrepo discussion:

1. submodule would incorporate a reference to the FFmpeg repository in 
MythTV. This would not work because we have many customizations of 
FFmpeg. It could work if we created first our own FFmpeg repository. I 
do not like that idea.

2. subtree includes a copy of FFmpeg's repo in our repo. We can 
customize the code as we need. We can also pull newer versions from 
FFmpeg and it will merge in the changes. Sometimes you may need to 
resolve conflicts if they have changed code that we have customized.

3. subrepo is a third party tool 
(https://github.com/ingydotnet/git-subrepo) that seems to be almost the 
same as subtree. One difference is that if you make a subsequent commit 
that includes changes to MythTV as well as to FFmpeg, subrepo separates 
them into two commits. It also keeps history of the subtrepo separate 
from the main history. My feeling about subrepo is that I would rather 
stick with built-in features of git (subtree) than rely on a third party 
addon that may not be supported in future.

I believe that using subtree or subrepo requires that we use the master 
branch of FFmpeg. I do not see a problem with using FFmpeg master 
together with MythTV master. The FFmpeg web page recommends using master 
if you are compiling FFmpeg yourself.

I will test subtree in my own repository first to make sure it behaves 
as expected.

Peter