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dgit-maint-merge(7) dgit dgit-maint-merge(7)

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:
  • 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-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 alioth.debian.org in addition to dgit-repos, you can do something like this:

    % git remote add -f origin git.debian.org:/git/collab-maint/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).

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 = %(version)s

    sign-tags = True
    pristine-tar = False
    pristine-tar-commit = False

Then we can import the upstream version:

    % git add debian/gbp.conf && git commit -m "create gbp.conf"
    % gbp import-orig ../foo_1.2.2.orig.tar.xz

You are now ready to proceed as above, making commits to both the upstream source and the debian/ directory.

If you want to maintain a copy of your repository on alioth.debian.org, you should push both the origin and the upstream branches:

    % git remote add -f origin git.debian.org:/git/collab-maint/foo.git
    % git push --follow-tags -u origin master upstream

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, 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.

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.

Alternatively, this text could be added to README.source. However, this might distract from more important information present in the latter file.

BUILDING AND UPLOADING

Use dgit build, dgit sbuild, dgit build-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

When upstream tags releases in git

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 remote update
    % git diff --stat 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
    % git deborig

and you are ready to try a build.

When upstream releases only tarballs

You will need the debian/gbp.conf from "When upstream releases only tarballs", above.

Then, either

    % gbp import-orig ../foo_1.2.2.orig.tar.xz

or if you have a working watch file

    % gbp import-orig --uscan

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@debian.org and the ftpmasters ftpmaster@ftp-master.debian.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:
1.
Create a new branch based off upstream's master branch.
2.
git-cherry-pick(1) commits from your master branch onto your new branch.
3.
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 git@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@spwhitton.name>. It contains contributions from other dgit contributors too - see the dgit copyright file.
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