Debian related goals for 2010

Here’s stuff that I’d like to do this year, more or less by decreasing order of importance:

  • translate my Debian book into English and get it published;
  • finish the cleanup of the perl API in dpkg-dev in order to create libdpkg-perl;
  • create dpkg-buildflags to export default build flags that packages should use (and get rid of the code setting those environment variables in dpkg-buildpackage), needed to properly fix #489771;
  • ensure the new source formats continue to gain acceptance by improving whatever is needed;
  • design a generic vcs-buildpackage infrastructure to be integrated in dpkg-dev. This design will probably happen through a DEP (Debian Enhancement Proposal) to ensure we have had proper discussion before someone gets to the implementation;
  • continue fixing dpkg bugs faster than they are reported;
  • enhance our infrastructure to ease interaction between contributors and to have a better view of how each package is maintained (see my last blog entry on this topic);
  • update the developers-reference where needed and fix some of the numerous wishlist bugs;
  • rewrite in C the last perl scripts provided by the dpkg binary package (update-alternatives/mksplit mainly, for dpkg-divert there’s a preliminary patch available already) so that it’s easier to build a minimal system without perl-base;
  • integrate the 3-way merge tool for Debian changelogs in dpkg-dev;

All of this probably doesn’t fit in my free time (being a father since last month does not help increasing my free time :-)), so if you’re interested in seeing one or more of those projects completed, and if you know some person/company that could sponsor them, get in touch with me!

New source formats allowed in testing/unstable

The ftpmasters merged my dak branch last week during their meeting and have enabled the support of new source formats “3.0 (quilt)” and “3.0 (native)” in testing, unstable and testing-proposed-updates. I have uploaded 3 packages using the new formats already: logidee-tools using “3.0 (native)”, quilt and ftplib using “3.0 (quilt)”. The latter is arch any and has been successfully built on all architectures even those that still use an old version of sbuild (it looks like the fears that the old version would not cope with the new format were unfounded). For logidee-tools I built it with “-Zbzip2” in order to use bzip2 compression on the native tarball.

I have updated the wiki page and the release goal page with latest information. Feel free to convert some of your packages to give it a try. For ftplib, it led me to discover a Debian specific patch that I completely missed when I took the package over. This is precisely the kind of benefit that I expect from generalizing this format, it will encourage us to have separate documented patches instead of keeping everything hidden inside the usual .diff.gz. Combined with DEP-3 (patch tagging guidelines), we have a better infrastructure to share our patches with the rest of the free software community.

The next step is to fix all bugs listed here and make dpkg-source use the new source formats by default (#553928). Feel free to help by preparing patches (and offering NMUs), it’s a release goal to have all packages buildable with new source formats.

3-way merge of Debian changelog files

I’ve been considering for some time now to create a merge tool specifically suited for debian/changelog files. My goal was to let Git use it automatically thanks to gitattributes.

I’ve just gone ahead, so let me introduce you git-merge-dch. Grab it with git clone git://git.debian.org/~hertzog/git-merge-dch.git, you can build a package if you wish. Beware, you need to have a dpkg-dev 1.15.5 that is not yet published (so you need to build dpkg from its git repository, git clone git://git.debian.org/dpkg/dpkg.git) as I rely on features that I introduced recently… you will also need the libalgorithm-merge-perl package.

Using it in a git repository requires two changes:

  • defining a new merge driver somewhere in the git configuration (in .git/config or ~/.gitconfig for example):
    [merge "git-merge-dch"]
            name = debian/changelog merge driver
            driver = git-merge-dch -m %O %A %B %A
    
  • defining the merge attribute for debian/changelog files either in .gitattributes in the repository itself or in .git/info/attributes:
    debian/changelog merge=git-merge-dch
    

Now you can safely maintain two branches of a package with changelog files evolving separately and merge one into the other without creating undue conflicts. Suppose you created an experimental branch for version 2.28 (you use a version 2.28-1~exp1) when 2.26.2 was current stable in the master branch. In the mean time, 2.26.3 got out and was packaged in master. Next time you merge stable into experimental, the changelog entries for 2.28 and 2.26.3 won’t collide despite being at the same place in the changelog file compared to the common ancestor.

Let’s continue with this example, 2.28 is out. Instead of adding a new changelog entry with “New upstream release” without further changes, you keep the current changelog entry and simply change the version into 2.28-1. While preparing this you discover a branch with fixes that was based on 2.28-1~exp1, if you merge it it will reintroduce a 2.28-1~exp1 entry that you don’t want. Fortunately you can use the --merge-prereleases (-m) option of git-merge-dch so that it strip the prerelease part of the version string and considers 2.28-1~exp1 and 2.28-1 to be the same entry really.

The only limitation is that this merge tool will remove any lines which are not parsed by Dpkg::Changelog (and which in theory are not supposed to be there).

Feel free to test, share your comments, report bugs and send patches!

Update: the script has been merged in dpkg-dev (>= 1.15.7) under the name dpkg-mergechangelogs.