This document describes elements of a workflow for using dgit to maintain an official Debian backport. We do not assume that whoever uploads the package to Debian unstable is using dgit.
The first time a package is backported for any particular Debian release, you will have to pass the --new option to dgit.
Let the master branch contain the packaging history uploaded to Debian unstable, and the buster-bpo branch be where you prepare your uploads to the buster-backports suite.
A merging backports workflow means that each time an upload migrates to Debian testing and you want to prepare an upload to buster-backports, you do something like this:
% git checkout buster-bpo % git merge master % dch --bpo % # any other changes needed for backporting % git commit -a % # try a build
A rebasing backports workflow means that you throw away the history of the buster-bpo branch each time a new version migrates to Debian testing, something equivalent to this:
% git checkout -B buster-bpo master % dch --bpo % # any other changes needed for backporting % git commit -a % # try a build
If you use a merging backports workflow, your changelog contains entries for each previous upload to buster-backports; in a rebasing workflow, it contains only the latest.
Choosing Between the Two Workflows
If backporting involves making no (additional) changes to the upstream source, whether you use a merging or rebasing backports workflow is a matter of personal preference. There are good arguments in favour of both workflows fitting the semantics of the *-backports suites.
If you have to make changes to the upstream source to make the package work on machines running Debian stable, it is advisable to choose a rebasing workflow. This ensures that dgit can automatically update the debian/patches directory without any manual intervention.
Tips for a Merging Workflow
Use dgit's branches
If you do not yourself upload the package to Debian unstable, it is usually easiest to use dgit's branches, and ignore the configured Vcs-Git repository.
You would use
% dgit clone foo bullseye
for a new backport of package 'foo' to buster-backports, and then
% dgit fetch bullseye % git merge dgit/dgit/bullseye
when new versions migrate to Debian testing.
Tips for a Rebasing Workflow
Use dgit's branches
If you do not yourself upload the package to Debian unstable, it is usually easiest to use dgit's branches, and ignore the configured Vcs-Git repository. For each new version from Debian testing, you would
% dgit fetch bullseye % git checkout -B buster-bpo dgit/dgit/bullseye % # use git-cherry-pick(1) to (re)apply any needed backporting fixes
dgit push tries hard to prevent you from accidentally overwriting uploads that it thinks aren't represented in the git history you are trying to upload. This is mainly to prevent accidentally overwriting NMUs.
With a rebasing backports workflow, dgit will think that every upload of a new version from Debian testing might be accidentally overwriting uploads. You will need to explicitly indicate the upload to buster-backports you wish to overwrite.
Suppose that the last upload to buster-backports was versioned 1.2.2-1~bpo10+1 and you have now prepared 1.2.3-1~bpo10+1 for upload. When you dgit push, you will need to pass --overwrite=1.2.2-1~bpo10+1.
Alternatively, you can perform the pseudomerge that --overwrite would have done yourself:
% dgit fetch buster-backports % git merge -s ours dgit/dgit/buster-backports % dgit push-source
dgit(1), dgit(7), https://backports.debian.org/
This manpage was written and is maintained by Sean Whitton <email@example.com>.