git help needed for 2.6.34 kernel branch revival

[Daniel Drake]

Hi,

I'm playing with a few forward-looking ideas, one of them being
upgrading OLPC's kernel from version 2.6.31 to 2.6.34. And always open
to learning more about git...

Now, a good while back, Deepak started working on a 2.6.34 branch,
presumably forked from the 2.6.31 one that we were working on at the
time. I'm not sure of the details of how the branch or merge was done.
http://dev.laptop.org/git/olpc-2.6/log/?h=olpc-2.6.34-dev

It would be nice to be able to use his work, given that it appears a
big chunk of the work is already done. But there are 2 complications:

 1. The 2.6.31 branch has seen a lot of developments and fixes since
the 2.6.34 branch was created. So, we need to pull in all the recent
changes that we've made in olpc-2.6.31.
 2. The olpc-2.6.31 branch has merged in a few of the 2.6.31.x
"linux-stable" releases; those familiar with kernel development will
understand that those releases are outside of Linus' official tree
(i.e. the 2.6.31 to 2.6.32 history in Linus' tree does *not* literally
include the 2.6.31.x releases)

If I try the obvious:
 git checkout olpc-2.6.34-dev
 git merge olpc-2.6.31

then we end up pulling in all of the linux-stable-2.6.31 changes into
the 2.6.34 branch. For the majority there will be no problem. But now
and then, fixes are made in -stable which differ from the equivalent
fixes that end up in mainline. For example
http://dev.laptop.org/git/olpc-2.6/commit/?h=olpc-2.6.31&id=5c7fba322917ef91842676de55fba470bc2af5f3
(note how it says "fixed in a different way")

So I end up with a large task on my hands (finding all these little
differences and figuring out the right course of action), and a
resultant kernel that I don't really trust.

Another option could be to undo the merges of the linux-stable trees
from olpc-2.6.31. But I don't know how.

What's the best course of action?


Perhaps the best answer is "start again with a 2.6.34 rebase". I can
use this command to determine all the OLPC commits that aren't in
mainline or the linux-stable merges:
git log --pretty=oneline 120f68c4..olpc-2.6.31
(120f68c4 is the 2.6.31.6 linux-stable release commit, the last
2.6.31-stable release merged into olpc-2.6.31)

Maybe this is the best course of action? The headache is that we're
looking at 399 commits.


On a separate note, I guess it would make sense for OLPC to define a
policy where -stable updates are not brought into the OLPC kernel
tree. This would avoid this headache in future, as the history would
flow consistent with Linus' tree.


Thoughts?

Thanks,
Daniel