dgit-maint-merge

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-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@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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