Re: How to cope with patches sanely
On Fri, 29 Feb 2008 16:11:48 +1300, Sam Vilain <firstname.lastname@example.org> said:
> Manoj Srivastava wrote:
>>> Yes. Feature branches are effectively forking a particular version
>>> of a project - this is not a problem, and is essential for efficient
>>> development. People jumbling together changes in "trunk" branches
>>> is perhaps one of the worst upshots of the 2002-2006 or so obsession
>>> with poorly designed centralised systems and in my opinion sank many
>> Err. If you go back and read this thread in the archive, You'll note
>> that I have stated that my feature branches are always kept up to
>> date with the latest upstream branch I am basing my Debian package
> This technique is also called rebasing the patch set; it's fine, but
> it's just one approach.
Actually, that is not it. I am not rebasing -- I am doing
repeated merges. Arch does not rebase -- it just applies the upstream
delta, with full history. This allows me to replay into the integration
branch at will.
>> When I have been creating patches for inclusion with upstream, I
>> essentially feed them the source patch and a changelog entry --
>> essentially, creating a single patch series; squashing the underlying
>> history. Most upstream do not care about the messy history of my
>> development; and most do not grok arch well enough to pull directly.
> This is sometimes worthwhile and sometimes a bad idea. The driving
> motive, if you want to aim for patches to be easily reviewed, is that
> each patch should introduce a single change, which is well explained.
> I agree that the upstream will not want a messy history; which is why
> you reshape the individual changes using a tool such as Quilt, Stacked
> Git, Guilt, Mercurial Queues, etc, so that they are more easily
I can do this by cherry picking the chnages from my topic
branch, and feeding it separately. Emacs and diff mode makes it easy to
split off chunks if I want to do it after the fact from the squashed
diff; or I can regenerate changesets and cherry pick the series.
And no, I can do this using plain old arch, and I don't really
have to change my SCM.
>>> They mean that a later merge back the other way, to merge the
>>> feature branch into the target branch, can happen painlessly.
>>> ASSUMING that you're using a system which has commutative merge
>>> characteristics, such as git or mercurial.
>> I use Arch.
> Arch is critically deficient in this respect; it doesn't really have a
> concept of tracking branches, and merging is not commutative; if you
> merge a branch that just merged from your branch, an unnecessary new
> changeset is made. But if you are rebasing then you don't need to
> worry about that. As I said, it's just more work.
Which is why we have sync-tree. Yes, I have to keep track myself
of which delta I am currently merging; and only apply a merge once
into each branch; and immedately syn-tree with the other branches.
And since it is all in one fully automated script, called
arch_upgrade, that takes any new upstream, updates all my topic branches
and my integration branch automatically, I don't see this as much more
Indeed, I have yet to see any porcelain that makes merging a
new upstream commit into all my topic branches and the integration
branch as a single operation, I suspect that it is more work in git; at
least until I can replicate my arch scaffolding for the git porcelain.
>>> Can you express this problem with reference to a particular history
>>> of an integration branch? I will provide some short git commands to
>>> extract the information in the form you are after.
>> Take any package. Say, flex. Or flex-old. You have all my feature
>> branches there. The --devo branch is the integration branch. Please
>> show me an automated way you can grab the feature branches and
>> generate a quilt series that gives you the devo branch. The diff.gz
>> is how we get from upstream to the devo branch (modulo ./debian); if
>> you can break that down nicely for the folks who want each feature
>> separate, that would work as well.
> Thanks for restating the problem clearly. While the underlying
> problem is easily approached and I would still call it trivial, the
> details of what you are asking for make it impossible - because quilt
> series cannot contain merges (someone correct me here if it can and I
> can go forward).
I don't use quilt, so I am not the one to answer this.
> Shipping changes for upstream inclusion as a *single* set of quilt
> patches is not possible if you are including merges, but if you allow
> the patches to be grouped, and introduce a new type of patch which
> encapsulates a merge (gitk has one example of this; it uses different
> identifiers to represent which file's lines are included), then it can
> be done. The apply-patches script would need extending to support
> this, but I don't think that's particularly show-stopping.
Great. This is, of course, a totally new proposal for debian
source package format; and one on which I hold no opinion; and will let
the interested parties and dpkg maintainers comment on it.
> However, ignoring the merges, so far we're not that far away from the
> "script" being 'git-log -p' or 'git format-patch upstreamrev'
But not all Debian maintainers are using git; and my workflow is
repeated and frequent cross merges, so it does not appear to be very
interesting to me either. But I am sure there are people who will
indeed find it useful.
> Also having never really used arch, if you can provide me with the
> commands to get a copy of those branches (the man page is sadly not
> very forthcoming), and I'll give the git-archimport script a whorl and
> see if I can get it imported and show how this can work in practice.
> If someone with git-archimport experience can perform this and publish
> the repositories somewhere, I'd be very grateful.
tla register-archive --present-ok http://arch.debian.org/arch/private/srivasta
tla grab http://arch.debian.org/arch/private/srivasta/grab/flex
This should grab a mostly empty directory structure in
my_version=$(tla versions -A email@example.com flex--upstream | tail -n 1)
if [ -n "$my_version" ]; then
my_branches=$(tla branches -A firstname.lastname@example.org flex)
if [[ -n "$my_branches" ]]; then
for branch in $(tla branches -A email@example.com flex |sort); do
my_bversion=$(tla versions -A firstname.lastname@example.org $branch | tail -n 1)
if [[ -n "$my_bversion" ]]; then
for version in $(tla versions -A email@example.com $branch | tail -n 1); do
test -d $version || tla get -A firstname.lastname@example.org $version $version
There. All branches, in one place.
>> If you code works well enough every single time a new upstream comes
>> around and I release a new version of flex or whatever, I'll throw in
>> the generated quilt patches.
> I think what is required is a rethink of the problem. What is being
> tried to be achieved, and are there any other ways to achieve it which
> will solve the problem in a vastly more effective way.
Remember, the problem is to create a new Debian source package
format that allows people using feature branches to present a set of
patches that other people are already using -- in other words, a quilt
If you propose a new patch format, you also have to convert a
quilt series into the same format (or perhaps your format
trivially reduces to a quilt series)
> Version control systems that have content-addressable filesystems
> (essentially, git and Monotone) are inherently efficient to
> distribute; as only the changes between versions need be distributed.
> The notion of stream compressing tarballs is archaic compared with
> being able to search for deltas anywhere in the source tree.
Which is great, but I fear it will not fly as a the one and only
> The essence of what I'm saying is to view a distributed git archive as
> a /replacement/ (or, if you prefer, complement) for the source
> archives; and going by previous results, this will result in an
> overall reduction of the size of the archive, faster distribution -
> even P2P - and preserving more history.
> Instead of distributing large source archive packages, the upstream
> sources are imported (perhaps as a tarball, or perhaps using a rich
> history-preserving git archive), and the patches are applied as
> commits on feature branches. When you 'apt-get source', you are
> simply checking out the head version (and probably the upstream as
> well). All the information you are after - individual changes from
> the upstream - are available. If the upstream updates, then the
> source archive can represent that in the most convenient fashion to
> the maintainer - be it a rebase of the applied patches as you have
> used previously, or a simple merge.
> And please, I'm not looking to start a VCS flamewar here - I'm talking
> about git in its capacity as a file distribution and archival
> At this task, it excels. It doesn't matter what the upstream uses;
> they can all be converted to git well.
Heh. More power to you, friend, for proposing git as the
replacement for wig & pen. I wish you luck.
May a hundred thousand midgets invade your home singing cheesy
lounge-lizard versions of songs from The Wizard of Oz.
Manoj Srivastava <email@example.com> <http://www.debian.org/~srivasta/>
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