On 5/2/19 2:33 PM, sean.brogan via groups.io wrote:
Brian,
I would really like to hear about the challenges your team faced and
issues that caused those solutions to be unworkable. Project Mu has and
continues to invest a lot in testing capabilities, build automation, and
finding ways to improve quality that scale.
Our products depend on a reference BIOS tree provided to us by a major
processor vendor. That tree includes portions of Edk2, plus numerous
proprietary additions. Each new platform starts with a new drop of
vendor code. They provide additional drops throughout the platform's
life. In the past these were distributed as zip files, but more
recently they have transitioned to git. We end up having to make
extensive changes to their code to port it to our platform. In
addition, we maintain internally several packages of code used on all
our platforms, designed to be platform-independent, plus a
platform-dependent package which is intended to be modified for each
platform.
When we first started using git, we looked for a way to share our
all-platform code among platforms, and move our platform-dependent code
easily to new platforms, while making it easy to integrate new drops
from our vendor. We considered using git submodules, but decided that
would be too awkward. Modifying code in a submodule involves committing
in the submodule, then committing in the module containing it. This
seemed like too much trouble for our developers, who were all new to
git. Plus, it didn't interact well at all with our internal bug
tracking system. Basically, there was no good way to tie commits in
various sub- and super-modules together in a straightforward, trackable way.
We tried a package called gitslave (http://gitslave.sourceforge.net/),
which automates running git commands across a super-repo and various
sub-repos, with some sugar for aggregating the results into a readable
whole. It's a bit more transparent than submodules. But at the end of
the day, you're still trying to coordinate multiple git repositories.
We gave it a try for a month or two, but having to manage multiple
repositories for day-to-day work, and the lack of a single commit
history spanning the entire tree doomed that scheme. Developers rebelled.
Ever since, we've used a single git repo per platform. We keep the
vendor code in a "base" branch, which we update as they provide drops,
then merge into our master branch. When we start a new platform, we use
git filter-branch to extract our all-platform and platform-dependent
code into a new branch, which we move to the new platform's repo and
merge into master. It's possible to re-extract the code if we need to
pick up updates. This doesn't provide total flexibility... for
instance, backporting a fix in our all-platform code back to a previous
platform involves manual cherrypicking. But for day-to-day development,
it lets us work in a single git tree, with a bisectable history, working
git-blame, commit IDs which tie directly to our bug tracker, and no
external tooling. It's a bit of a pain to merge a new drop (shell
scripts are our friends), but we're optimizing for ease of local
development. That seems like the best use of our resources.
So I'm leery of any scheme which involves multiple repos managed by an
external tool. It sounds like a difficult way to do day-to-day
development. If Edk2 does move to split repos, we could filter-branch
and merge them all together into a single branch for internal use, I
suppose. But that does make it harder to push fixes upstream. (Not
that we end up doing a lot of that... we're not developing an
open-source BIOS, just making use of open-source upstream components.
So our use case is quite a bit different from Laszlo's.) We're also
generally focusing on one platform at a time, not trying to update
shared code across many at once. So our use case may be different from
Sean's.
This got rather long... I hope it helps explain where we're coming from.
--
Brian J. Johnson
Enterprise X86 Lab
Hewlett Packard Enterprise
brian.john...@hpe.com
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