Introduction and Scope
This tutorial describes how a Debian Developer can do a straightforward NMU of a package in Debian, using dgit.
This document won't help you decide whether an NMU is a good idea or whether it be well received. The Debian Developers' Reference has some (sometimes questionable) guidance on this.
Conversely, you do not need to know anything about the usual maintainer's git workflow. If appropriate, you can work on many different packages, making similar changes, without worrying about the individual maintainers' git practices.
This tutorial only covers changes which can sensibly be expressed as a reasonably small number of linear commits (whether to Debian packaging or to upstream files or both).
If you want to do a new upstream version, you probably want to do as the maintainer would have done. You'll need to find out what the maintainer's git practices are and consult the appropriate
dgit-maint-*(7) workflow tutorial,
% dgit clone glibc jessie % cd glibc % git am ~/glibc-security-fix.diff % dch --nmu "Apply upstream's fix for foo bug." % git add debian/changelog && git commit -m"NMU changelog entry" % dpkg-buildpackage -uc -b [ run your tests ] % dch -r && git add debian/changelog && git commit -m"Finalise NMU" % dgit -wgf sbuild -A -c jessie [ final tests on generated .debs ] % dgit -wgf [--delayed=5] push jessie [ enter your gnupg passphrase as prompted ] [ see that push and upload are successful ] [ prepare and email NMU diff (git-diff, git-format-patch) ]
What Kind of Changes and Commits to Make
When preparing an NMU, the git commits you make on the dgit branch should be simple linear series of commits with good commit messages. The commit messages will be published in various ways, including perhaps being used as the cover messages for generated quilt patches.
Do not make merge commits. Do not try to rebase to drop patches - if you need to revert a change which is actually a Debian patch, use git-revert.
If you need to modify a Debian patch, make a new commit which fixes what needs fixing, and explain in the commit message which patch it should be squashed with (perhaps by use of a commit message in
git rebase --autosquash -i format).
(Of course if you have specific instructions from the maintainer, you can follow those instead. But the procedure in this tutorial is legitimate for any maintainer, in the sense that it should generate an upload to which the maintainer cannot reasonably object.)
dgit clone will put you on a branch like
dgit/sid. There is a pseudo-remote called
dgit which also contains a branch like
dgit/sid, so you do things like
git diff dgit/dgit/sid to see what changes you have made.
Keeping Your Working Tree Tidy
Don't forget to
git add any new files you create. Otherwise git clean (which is requested with the
-wgf option in the recipe above) will delete them.
Many package builds leave dirty git trees. So, commit before building. That way you can use
git reset --hard.
If you follow this approach you don't need to care about the build dirtying the tree. It also means you don't care about the package clean target, which is just as well because many package clean targets are broken.
Other Git Branches
The dgit git history (visible in gitk and git log) is not necessarily related to the maintainer's or upstream's git history (if any).
If the maintainer has advertised a git repo with Vcs-Git dgit will set up a remote for it, so you can do
% git fetch vcs-git
You can cherry pick changes from there, for example. Note that the maintainer's git history may not be suitable for use with dgit. For example, it might be a patches-unapplied branch or even contain only a debian/ directory.
Uploading to Delayed
You can use dgit's --delayed option to upload to the DELAYED queue. However, you should read the warning about this option in dgit(1).
dgit(1), dgit(7), dgit-maint-*(7)
dgit(1), dgit-maint-debrebase(7), dgit-maint-gbp(7), dgit-sponsorship(7), dgit-user(7).