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NAME

dgit - tutorial for package maintainers, using a workflow centered around git-merge(1)

INTRODUCTION

This document describes elements of a workflow for maintaining a non-native Debian package using dgit. The workflow makes the following opinionated assumptions:

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.

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).

INITIAL DEBIANISATION

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

It can be a good idea to compare upstream’s released tarballs with the release tags, at least for the first upload of the package. If they are different, you might need to add some additional steps to your debian/rules, such as running autotools.

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

Sometimes upstream does not tag their releases, or you want to package an unreleased git snapshot. In such a case you can create your own upstream release tag, of the form upstream/ver, where ver is the upstream version you plan to put in debian/changelog. The upstream/ prefix ensures that your tag will not clash with any tags upstream later creates.

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.

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 CONFIGURATION

debian/source/options
We set some source package options such that dgit can transparently handle the "dropping" and "refreshing" of changes to the upstream source:

    single-debian-patch
    auto-commit

You don’t need to create this file if you are using the version 1.0 source package format.

Sample text for debian/source/patch-header
It is a good idea to explain how a user can obtain a breakdown of the changes to the upstream source:

The Debian packaging of foo is maintained in git, using the merging workflow described in dgit-maint-merge(7). There isn’t a patch queue that can be represented as a quilt series.

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.

If you are using the version 1.0 source package format, this text should be added to README .source instead. The version 1.0 source package format ignores debian/source/patch-header.

If you’re using the version 3.0 (quilt) source package format, you could add this text to README .source instead of debian/source/patch-header, but this might distract from more important information present in README .source.

BUILDING AND UPLOADING

Use dgit build, dgit sbuild, dgit pbuilder, dgit cowbuilder, dgit push-source, and dgit push 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 an 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.

Then, either

    % 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 dgit-owner [AT] debian.org and the ftpmasters ftpmaster [AT] ftp-master.org).

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:

For example (and it is only an example):

    % # fork foo.git on GitHub
    % git remote add -f fork git [AT] github.com: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.

INCORPORATING NMUS

    % dgit pull

Alternatively, you can apply the NMU diff to your repository. The next push will then require --overwrite.

SEE ALSO

dgit(1), dgit(7)

AUTHOR

This tutorial was written and is maintained by Sean Whitton <spwhitton [AT] spwhitton.name>. It contains contributions from other dgit contributors too - see the dgit copyright file.