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Comment by IshKebab | Hacker News Reader

What is patch quilting, for the blissfully unaware?

https://wiki.debian.org/UsingQuilt but the short form is that you keep the original sources untouched, then as part of building the package, you apply everything in a `debian/patches` directory, do the build, and then revert them. Sort of an extreme version of "clearly labelled changes" - but tedious to work with since you need to apply, change and test, then stuff the changes back into diff form (the quilt tool uses a push/pop mechanism, so this isn't entirely mad.)

Ha yes that does sound mad. If only there was a version control system specifically designed to track changes to code...

it's quite difficult to maintain a quilt like workflow with plain git

I've tried it

Quilt is difficult to maintain, but a quilt-like workflow? Easy: it's just a branch with all patches as commits. You can re-apply those to new releases of the upstream by using `git rebase --onto $new_upstream_commit_tag_or_branch`.

Those who don't understand git are doomed to reimplement half of it poorly?

(I know that's not quite the Greenspun quote)

I think that's right, sadly.

How do you track changes to the patches themselves?

You can keep the old branches around if you want. Or merge instead of rebasing.

By having a naming convention for your tags and branches, then you can always identify the upstream "base" upon which the Debian "patches" are based, and then you can trivially use `git log` to list them.

Really, Git has a solution to this. If you insist that it doesn't without looking, you'll just keep re-inventing the wheel badly.

but then if I want to see the history for a specific patch, or bisect them?

mercurial has a patch queue extension that married it and quilt, which was very easy to use

Do you ever really want this? I don't recall wanting this. But you can still get this: just list the ${base_ref}..${deb_ref} commit ranges, select the commit you want, and diff the `git show` of the selected commits. It helps here to keep the commit synopsis the same.

E.g.,

  c0=$(git log --oneline ${base_ref0}..${deb_ref0} |
         grep "^[^ ] The subject in question" |
         cut -d' ' -f1)
  c1=$(git log --oneline ${base_ref1}..${deb_ref1} |
         grep "^[^ ] The subject in question" |
         cut -d' ' -f1)
  if [[ -z $c0 || -z $c1 ]]; then
    echo "Error: commits not found"
  else
    diff -ubw <(git show $c0) <(git show c1)
  fi

See also the above commentary about Gerrit and commit IDs.

(Honestly I don't need commit IDs. What happens if I eventually split a commit in a patch series into two? Which one, if either, gets the old commit ID? So I just don't bother.)

So there’s no way to have commit messages on changes to patches? There’s also https://dep-team.pages.debian.net/deps/dep3/

People keep saying “just use Git commits” without understanding the advantages of the Quilt approach. There are tools to keep patches as Git commits that solve this, but “just Git commits” do not.

Having maintained private versions of Debian packages, I have zero need for "commit messages on changes to patches". I can diff them as needed as I showed, but I rarely ever need to -- I mostly only rebase onto new upstreams. Seeing differences in patches isn't helpful because there is not enough context there as to what changed in the upstreams.

I rather suspect that "commit messages on changes to patches" is what Debian ended up with and back-justifies it.

Of course, I am not a Debian maintainer, so it's entirely possible I'm just missing the experience of it that would make me want "commit messages on changes to patches".

Quilt was AFAIK used before Git, so you’re not wrong. But now that it’s there, it has some advantages.

I’m not arguing against replacing Quilt, but it should be more than just Git. I haven’t done Debian packaging in a long time but apparently there are some Git-based tools now?

I don't know that I've ever wanted to diff a diff, but you could do that still. And bisecting would still be possible, especially if you use merges instead of rebases.

Bisect rebases... you mean that you have two release branches based on divergent upstream branches and you want to quickly test where a bug was introduced on the way from the one to the other? What I would do in a rebase workflow is find the merge base (`git merge-base`) of the two release branches, and bisect from that to the release branch I'm interested in.

Quilt predates Git. Back then source was distributed as a tarball, and Debian simply maintained a directory full of patches to apply to the tarball.

Sure but Git has been available (and super popular) for almost 20 years now.

So has git-buildpackage; the debian historical archives don't go further back than v0.4, but the oldest bug report referencing gbp is from december 2006: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=403987

Yea, so? Debian goes back 32 or more years, and quilt dates to approximately the same time. It’s probably just a year or two younger than Debian.

At Mozilla some developers used quilt for local development back when the Mozilla Suite source code was kept in a CVS repository. CVS had terrible support for branches. Creating a branch required writing to each individual ,v file on the server (and there was one for every file that had existed in the repository, plus more for the ones that had been deleted). It was so slow that it basically prevented anyone from committing anything for hours while it happened (because otherwise the branch wouldn’t necessarily get a consistent set of versions across the commit), so feature branches were effectively impossible. Instead, some developers used quilt to make stacks of patches that they shared amongst their group when they were working on larger features.

Personally I didn’t really see the benefit back then. I was only just starting my career, fresh out of university, and hadn’t actually worked on any features large enough to require months of work, multiple rounds of review, or even multiple smaller commits that you would rebase and apply fixups to. All I could see back then were the hoops that those guys were jumping through. The hoops were real, but so were the benefits.

> Yea, so?

So it's clearly a way better solution and it's disappointing that they still haven't switched to it after 20 years? I dunno what else to say...

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