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

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-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.

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 CONFIGURATION

   dgit 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 command should be executed in each git clone of this package, including your co-
       maintainer's.  Don't set it more globally, because it is not a good default for working on
       Debian source packages in general.

   debian/source/options
       We set a source package option to help dpkg handle changes to the upstream source:

           auto-commit

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

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.

       If you want to upload with git-debpush(1), for the first upload you should pass the
       --quilt=single quilt mode option (see git-debpush(1)).

       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.

       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@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.

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.