dgit - tutorial for package maintainers, using a workflow centered around git-merge(1)
This document describes elements of a workflow for maintaining a non-native Debian package using dgit. The workflow makes the following opinionated assumptions:
- Git histories should be the non-linear histories produced by git-merge(1), preserving all information about divergent development that was later brought together.
- Maintaining convenient and powerful git workflows takes priority over the
usefulness of the raw Debian source package. The Debian archive is thought
of as an output format.
For example, we don't spend time curating a series of quilt patches. However, in straightforward cases, the information such a series would contain is readily available from dgit-repos.
- It is more important to have the Debian package's git history be a descendent of upstream's git history than to use exactly the orig.tar that upstream makes available for download.
This workflow is less suitable for some packages. When the Debian delta contains multiple pieces which interact, or which you aren't going to be able to upstream soon, it might be preferable to maintain the delta as a rebasing patch series. For such a workflow see for example dgit-maint-debrebase(7) and dgit-maint-gbp(7).
This section explains how to start using this workflow with a new package. It should be skipped when converting an existing package to this workflow.
When upstream tags releases in git¶
Suppose that the latest stable upstream release is 1.2.2, and this has been tagged '1.2.2' by upstream.
% git clone -oupstream https://some.upstream/foo.git % cd foo % git verify-tag 1.2.2 % git reset --hard 1.2.2 % git branch --unset-upstream
The final command detaches your master branch from the upstream remote, so that git doesn't try to push anything there, or merge unreleased upstream commits. If you want to maintain a copy of your packaging branch on salsa.debian.org in addition to dgit-repos, you can do something like this:
% git remote add -f origin salsa.debian.org:Debian/foo.git % git push --follow-tags -u origin master
Now go ahead and Debianise your package. Just make commits on the master branch, adding things in the debian/ directory. If you need to patch the upstream source, just make commits that change files outside of the debian/ directory. It is best to separate commits that touch debian/ from commits that touch upstream source, so that the latter can be cherry-picked by upstream.
Note that there is no need to maintain a separate 'upstream' branch, unless you also happen to be involved in upstream development. We work with upstream tags rather than any branches, except when forwarding patches (see FORWARDING PATCHES UPSTREAM, below).
Finally, you need an orig tarball:
% git deborig
See git-deborig(1) if this fails.
This tarball is ephemeral and easily regenerated, so we don't commit it anywhere (e.g. with tools like pristine-tar(1)).
Verifying upstream's tarball releases
A convenient way to perform this check is to import the tarball as described in the following section, using a different value for 'upstream-tag', and then use git-diff(1) to compare the imported tarball to the release tag. If they are the same, you can use upstream's tarball instead of running git-deborig(1).
Using untagged upstream commits
For example, suppose that the latest upstream release is 1.2.2 and you want to package git commit ab34c21 which was made on 2013-12-11. A common convention is to use the upstream version number 1.2.2+git20131211.ab34c21 and so you could use
% git tag -s upstream/1.2.2+git20131211.ab34c21 ab34c21
to obtain a release tag, and then proceed as above.
One can generate such a versioned tag using git show's --pretty option. e.g.:
% git tag -s upstream/$(git show --date=format:%Y%m%d --pretty=format:"1.2.2+git%cd.%h" --quiet upstream/main) upstream/main
When upstream releases only tarballs¶
We need a virtual upstream branch with virtual release tags. gbp-import-orig(1) can manage this for us. To begin
% mkdir foo % cd foo % git init
Now create debian/gbp.conf:
[DEFAULT] upstream-branch = upstream debian-branch = master upstream-tag = upstream/%(version)s sign-tags = True pristine-tar = False pristine-tar-commit = False [import-orig] merge-mode = merge merge = False
gbp-import-orig(1) requires a pre-existing upstream branch:
% git add debian/gbp.conf && git commit -m "create gbp.conf" % git checkout --orphan upstream % git rm -rf . % git commit --allow-empty -m "initial, empty branch for upstream source" % git checkout -f master
Then we can import the upstream version:
% gbp import-orig --merge --merge-mode=replace ../foo_1.2.2.orig.tar.xz
Our upstream branch cannot be pushed to dgit-repos, but since we will need it whenever we import a new upstream version, we must push it somewhere. The usual choice is salsa.debian.org:
% git remote add -f origin salsa.debian.org:Debian/foo.git % git push --follow-tags -u origin master upstream
You are now ready to proceed as above, making commits to both the upstream source and the debian/ directory.
CONVERTING AN EXISTING PACKAGE¶
This section explains how to convert an existing Debian package to this workflow. It should be skipped when debianising a new package.
No existing git history¶
% dgit clone foo % cd foo % git remote add -f upstream https://some.upstream/foo.git
Existing git history using another workflow¶
First, if you don't already have the git history locally, clone it, and obtain the corresponding orig.tar from the archive:
% git clone git.debian.org:collab-maint/foo % cd foo % origtargz
Now dump any existing patch queue:
% git rm -rf debian/patches % git commit -m "drop existing quilt patch queue"
Then make new upstream tags available:
% git remote add -f upstream https://some.upstream/foo.git
Now you simply need to ensure that your git HEAD is dgit-compatible, i.e., it is exactly what you would get if you ran dpkg-buildpackage -i'(?:^|/)\.git(?:/|$)' -I.git -S and then unpacked the resultant source package.
To achieve this, you might need to delete debian/source/local-options. One way to have dgit check your progress is to run dgit build-source.
The first dgit push will require --overwrite. If this is the first ever dgit push of the package, consider passing --deliberately-not-fast-forward instead of --overwrite. This avoids introducing a new origin commit into your git history. (This origin commit would represent the most recent non-dgit upload of the package, but this should already be represented in your git history.)
SOURCE PACKAGE AND GIT WORKING TREE CONFIGURATION¶
We must tell dgit not to try to maintain a linear queue of patches to the upstream source:
git config dgit.default.quilt-mode single
This affects only this one git tree; your other git trees for this package (and co-maintainers) will need it too. Don't set it more globally, because the maintainers of any other packages you work on, or send patches for, may be offended by its effects.
We set a source package option to help dpkg handle changes to the upstream source:
You don't need to create this file if you are using the version 1.0 source package format.
Sample text for debian/README.source¶
It is a good idea to explain how a user can obtain a breakdown of the changes to the upstream source:
A detailed breakdown of the changes is available from their canonical representation - git commits in the packaging repository. For example, to see the changes made by the Debian maintainer in the first upload of upstream version 1.2.3, you could use:
% git clone https://git.dgit.debian.org/foo % cd foo % git log --oneline 1.2.3..debian/1.2.3-1 -- . ':!debian'
(If you have dgit, use `dgit clone foo`, rather than plain `git clone`.)
A single combined diff, containing all the changes, follows.
BUILDING AND UPLOADING¶
Use dgit build, dgit sbuild, dgit pbuilder, dgit cowbuilder, dgit push-source, and dgit push-built as detailed in dgit(1). If any command fails, dgit will provide a carefully-worded error message explaining what you should do. If it's not clear, file a bug against dgit. Remember to pass --new for the first upload.
As another alternative to dgit build and friends, you can use a tool like gitpkg(1). This works because like dgit, gitpkg(1) enforces that HEAD has exactly the contents of the source package. gitpkg(1) is highly configurable, and one dgit user reports using it to produce and test multiple source packages, from different branches corresponding to each of the current Debian suites.
If you want to skip dgit's checks while iterating on a problem with the package build (for example, you don't want to commit your changes to git), you can just run dpkg-buildpackage(1) or debuild(1) instead.
NEW UPSTREAM RELEASES¶
Obtaining the release¶
When upstream tags releases in git
% git fetch --tags upstream
If you want to package an untagged upstream commit (because upstream does not tag releases or because you want to package an upstream development snapshot), see "Using untagged upstream commits" above.
When upstream releases only tarballs
You will need the debian/gbp.conf from "When upstream releases only tarballs", above. You will also need your upstream branch. Above, we pushed this to salsa.debian.org. You will need to clone or fetch from there, instead of relying on dgit clone/dgit fetch alone.
% gbp import-orig ../foo_1.2.3.orig.tar.xz
or if you have a working watch file
% gbp import-orig --uscan
In the following, replace 1.2.3 with upstream/1.2.3.
Reviewing & merging the release¶
It's a good idea to preview the merge of the new upstream release. First, just check for any new or deleted files that may need accounting for in your copyright file:
% git diff --name-status --diff-filter=ADR master..1.2.3 -- . ':!debian'
You can then review the full merge diff:
% git merge-tree `git merge-base master 1.2.3` master 1.2.3 | $PAGER
Once you're satisfied with what will be merged, update your package:
% git merge 1.2.3 % dch -v1.2.3-1 New upstream release. % git add debian/changelog && git commit -m changelog
If you obtained a tarball from upstream, you are ready to try a build. If you merged a git tag from upstream, you will first need to generate a tarball:
% git deborig
HANDLING DFSG-NON-FREE MATERIAL¶
When upstream tags releases in git¶
We create a DFSG-clean tag to merge to master:
% git checkout -b pre-dfsg 1.2.3 % git rm evil.bin % git commit -m "upstream version 1.2.3 DFSG-cleaned" % git tag -s 1.2.3+dfsg % git checkout master % git branch -D pre-dfsg
Before merging the new 1.2.3+dfsg tag to master, you should first determine whether it would be legally dangerous for the non-free material to be publicly accessible in the git history on dgit-repos.
If it would be dangerous, there is a big problem; in this case please consult your archive administrators (for Debian this is the dgit administrator firstname.lastname@example.org and the ftpmasters email@example.com).
When upstream releases only tarballs¶
The easiest way to handle this is to add a Files-Excluded field to debian/copyright, and a uversionmangle setting in debian/watch. See uscan(1). Alternatively, see the --filter option detailed in gbp-import-orig(1).
FORWARDING PATCHES UPSTREAM¶
The basic steps are:
- Create a new branch based off upstream's master branch.
- git-cherry-pick(1) commits from your master branch onto your new branch.
- Push the branch somewhere and ask upstream to merge it, or use git-format-patch(1) or git-request-pull(1).
For example (and it is only an example):
% # fork foo.git on GitHub % git remote add -f fork firstname.lastname@example.org:spwhitton/foo.git % git checkout -b fix-error upstream/master % git config branch.fix-error.pushRemote fork % git cherry-pick master^2 % git push % # submit pull request on GitHub
Note that when you merge an upstream release containing your forwarded patches, git and dgit will transparently handle "dropping" the patches that have been forwarded, "retaining" the ones that haven't.
% dgit pull
Alternatively, you can apply the NMU diff to your repository. The next push will then require --overwrite.
This tutorial was written and is maintained by Sean Whitton <email@example.com>. It contains contributions from other dgit contributors too - see the dgit copyright file.
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