dgit - principles of operation
treats the Debian archive as a version control system, and
bidirectionally gateways between the archive and git. The git view of the
package can contain the usual upstream git history, and will be augmented by
commits representing uploads done by other developers not using dgit. This git
history is stored in a canonical location known as dgit-repos
lives on a dedicated git server.
git branches suitable for use with dgit can be edited directly in git, and used
directly for building binary packages. They can be shared using all
conventional means for sharing git branches. It is not necessary to use dgit
to work with dgitish git branches. However, dgit is (usually) needed in order
to convert to or from Debian-format source packages.
- Reference manual and documentation catalogue.
- Tutorials and workflow guides. See dgit(1) for a list.
You may use any suitable git workflow with dgit, provided you satisfy dgit's
dgit maintains a pseudo-remote called dgit
, with one branch per suite.
This remote cannot be used with plain git.
repository for each package contains one ref per suite
. These should be pushed to only by dgit.
They are fast forwarding. Each push on this branch corresponds to an upload
(or attempted upload).
However, it is perfectly fine to have other branches in dgit-repos; normally the
dgit-repos repo for the package will be accessible via the remote name
dgit push will also make signed tags called archive/debian/version
(with version encoded a la DEP-14) and push them to dgit-repos. These are used
at the server to authenticate pushes.
Uploads made by dgit contain an additional field Dgit
in the source
package .dsc. (This is added by dgit push.) This specifies: a commit (an
ancestor of the dgit/suite branch) whose tree is identical to the unpacked
source upload; the distro to which the upload was made; a tag name which can
be used to fetch the git commits; and a url to use as a hint for the dgit git
server for that distro.
Uploads not made by dgit are represented in git by commits which are synthesised
by dgit. The tree of each such commit corresponds to the unpacked source;
there is a commit with the contents, and a pseudo-merge from last known upload
- that is, from the contents of the dgit/suite branch. Depending on the source
package format, the contents commit may have a more complex structure, but
ultimately it will be a convergence of stubby branches from origin commits
representing the components of the source package.
dgit expects trees that it works with to have a dgit
This refers to the dgit-created git view of the corresponding archive.
The dgit archive tracking view is synthesised locally, on demand, by each copy
of dgit. The tracking view is always a descendant of the dgit-repos suite
branch (if one exists), but may be ahead of it if uploads have been done
without dgit. The archive tracking view is always fast forwarding within each
dgit push can operate on any commit which is a descendant of the suite tracking
dgit does not make a systematic record of its imports of orig tarball(s). So it
does not work by finding git tags or branches referring to orig tarball(s).
The orig tarballs are downloaded (by dgit clone) into the parent directory, as
with a traditional (non-gitish) dpkg-source workflow. You need to retain these
tarballs in the parent directory for dgit build and dgit push. (They are not
needed for purely-git-based workflows.)
dgit repositories could be cloned with standard (git) methods. However, the dgit
repositories do not contain uploads not made with dgit. And for sourceful
builds / uploads the orig tarball(s) will need to be present in the parent
To a user looking at the archive, changes pushed in a simple NMU using dgit look
like reasonable changes made in an NMU: in a `3.0 (quilt)' package the delta
from the previous upload is recorded in new patch(es) constructed by
dgit can synthesize a combined view of several underlying suites. This is
requested by specifying, for suite,
a comma-separated list:
This facility is available with dgit clone, fetch and pull, only.
dgit will fetch the same package from each specified underlying suite,
separately (as if with dgit fetch). dgit will then generate a pseudomerge
commit on the tracking branch remotes/dgit/dgit/suite
the tip of each of the underlying suites as an ancestor, and which contains
the same as the suite which has the highest version of the package.
The package must exist in mainsuite, but need not exist in the subsuites.
If a specified subsuite starts with -
then mainsuite is prepended.
So, for example, stable,-security
means to look for the package in
stable, and stable-security, taking whichever is newer. If stable is currently
jessie, dgit clone would leave you on the branch dgit/jessie,-security
Combined suites are not supported by the dgit build operations. This is because
those options are intended for building for uploading source packages, and
look in the changelog to find the relevant suite. It does not make sense to
name a dgit-synthesised combined suite in a changelog, or to try to upload to
When using this facility, it is important to always specify the same suites in
the same order: dgit will not be make a coherent fast-forwarding history view
The history generated by this feature is not normally suitable for merging back
into upstreams, as it necessarily contains unattractive pseudomerges.
Because the synthesis of the suite tracking branches is done locally based only
on the current archive state, it will not necessarily see every upload not
done with dgit. Also, different versions of dgit (or the software it calls)
might import the same .dscs differently (although we try to minimise this). As
a consequence, the dgit tracking views of the same suite, made by different
instances of dgit, may vary. They will have the same contents, but may have
There is no uniform linkage between the tracking branches for different suites.
The Debian infrastructure does not do any automatic import of uploads made
without dgit. It would be possible for a distro's infrastructure to do this;
in that case, different dgit client instances would see exactly the same
There has been no bulk import of historical uploads into Debian's dgit
infrastructure. To do this it would be necessary to decide whether to import
existing vcs history (which might not be faithful to dgit's invariants) or
previous non-Dgit uploads (which would not provide a very rich history).
Distros which do not maintain a set of dgit history git repositories can still
be used in a read-only mode with dgit. Currently Ubuntu is configured this
git has features which can automatically transform files as they are being
copied between the working tree and the git history. The attributes can be
specified in the source tree itself, in .gitattributes
These transformations are context-sensitive and not, in general, reversible, so
dgit operates on the principle that the dgit git history contains the actual
contents of the package. (When dgit is manipulating a .dsc, it does so in a
private area, where the transforming gitattributes are defused, to achieve
If transforming gitattributes are used, they can cause trouble, because the
working tree files can differ from the git revision history (and therefore
from the source packages). dgit warns if it finds a .gitattributes file (in a
package being fetched or imported), unless the transforming gitattributes have
dgit clone and dgit setup-new-tree disable transforming gitattributes by
default, by creating a suitable .git/info/attributes. See dgit
and dgit setup-gitattributes
If you are not the maintainer, you do not need to worry about the source format
of the package. You can just make changes as you like in git. If the package
is a `3.0 (quilt)' package, the patch stack will usually not be represented in
the git history.
For a format `3.0 (quilt)' source package, dgit may have to make a commit on
your current branch to contain metadata used by quilt and dpkg-source.
This is because `3.0 (quilt)' source format represents the patch stack as files
in debian/patches/ actually inside the source tree. This means that, taking
the whole tree (as seen by git or ls) (i) dpkg-source cannot represent certain
trees, and (ii) packing up a tree in `3.0 (quilt)' and then unpacking it does
not always yield the same tree.
dgit will automatically work around this for you when building and pushing. The
only thing you need to know is that dgit build, sbuild, etc., may make new
commits on your HEAD. If you're not a quilt user this commit won't contain any
changes to files you care about.
You can explicitly request that dgit do just this fixup, by running dgit
If you are a quilt user you need to know that dgit's git trees are `patches
applied packaging branches' and do not contain the .pc directory (which is
used by quilt to record which patches are applied). If you want to manipulate
the patch stack you probably want to be looking at tools like git-dpm.
When working with git branches intended for use with the `3.0 (quilt)' source
format dgit can automatically convert a suitable maintainer-provided git
branch (in one of a variety of formats) into a dgit branch.
When a split view mode is engaged dgit build commands and dgit push will, on
each invocation, convert the user's HEAD into the dgit view, so that it can be
built and/or uploaded.
dgit push in split view mode will push the dgit view to the dgit git server. The
dgit view is always a descendant of the maintainer view. dgit push will also
make a maintainer view tag according to DEP-14 and push that to the dgit git
Split view mode must be enabled explicitly (by the use of the applicable command
line options, subcommands, or configuration). This is because it is not
possible to reliably tell (for example) whether a git tree for a dpkg-source
`3.0 (quilt)' package is a patches-applied or patches-unapplied tree.
Split view conversions are cached in the ref dgit-intern/quilt-cache. This
should not be manipulated directly.
This section is mainly of interest to maintainers who want to use dgit with
their existing git history for the Debian package.
Some developers like to have an extra-clean git tree which lacks files which are
normally found in source tarballs and therefore in Debian source packages. For
example, it is conventional to ship ./configure in the source tarball, but
some people prefer not to have it present in the git view of their project.
dgit requires that the source package unpacks to exactly the same files as are
in the git commit on which dgit push operates. So if you just try to dgit push
directly from one of these extra-clean git branches, it will fail.
As the maintainer you therefore have the following options:
- Delete the files from your git branches, and your Debian
source packages, and carry the deletion as a delta from upstream. (With
`3.0 (quilt)' this means represeting the deletions as patches. You may
need to pass --include-removal to dpkg-source --commit, or pass
corresponding options to other tools.) This can make the Debian source
package less useful for people without Debian build infrastructure.
- Persuade upstream that the source code in their git history
and the source they ship as tarballs should be identical. Of course simply
removing the files from the tarball may make the tarball hard for people
- One answer is to commit the (maybe autogenerated) files,
perhaps with some simple automation to deal with conflicts and spurious
changes. This has the advantage that someone who clones the git repository
finds the program just as easy to build as someone who uses the
Of course it may also be that the differences are due to build system bugs,
which cause unintended files to end up in the source package. dgit will notice
this and complain. You may have to fix these bugs before you can unify your
existing git history with dgit's.
Some upstream tarballs contain build artifacts which upstream expects some users
not to want to rebuild (or indeed to find hard to rebuild), but which in
Debian we always rebuild.
Examples sometimes include crossbuild firmware binaries and documentation. To
avoid problems when building updated source packages (in particular, to avoid
trying to represent as changes in the source package uninteresting or perhaps
unrepresentable changes to such files) many maintainers arrange for the
package clean target to delete these files.
dpkg-source does not (with any of the commonly used source formats) represent
deletion of binaries (outside debian/) present in upstream. Thus deleting such
files in a dpkg-source working tree does not actually result in them being
deleted from the source package. Thus deleting the files in rules clean sweeps
this problem under the rug.
However, git does always properly record file deletion. Since dgit's principle
is that the dgit git tree is the same of dpkg-source -x, that means that a
dgit-compatible git tree always contains these files.
For the non-maintainer, this can be observed in the following suboptimal
- The package clean target often deletes these files, making
the git tree dirty trying to build the source package, etc. This can be
fixed by using dgit -wg aka --clean=git, so that the package
clean target is never run.
- The package build modifies these files, so that builds make
the git tree dirty. This can be worked around by using `git reset --hard'
after each build (or at least before each commit or push).
From the maintainer's point of view, the main consequence is that to make a
dgit-compatible git branch it is necessary to commit these files to git. The
maintainer has a few additional options for mitigation: for example, it may be
possible for the rules file to arrange to do the build in a temporary area,
which avoids updating the troublesome files; they can then be left in the git
tree without seeing trouble.
A related problem is other unexpected behaviour by a package's clean
target. If a package's rules modify files which are distributed in the
package, or simply forget to remove certain files, dgit will complain that the
tree is dirty.
Again, the solution is to use dgit -wg
instructs dgit to use git clean instead of the package's build target, along
with perhaps git reset --hard
before each build.
This is 100% reliable, but has the downside that if you forget to git add or to
commit, and then use dgit -wg
or git reset --hard
, your changes
may be lost.