Posts tagged 'vcs'

Silver Platter

Making changes across the open source ecosystem is very hard; software is hosted on different platforms and in many different version control repositories. Not being able to make bulk changes slows down the rate of progress. For example, instead of being able to actively run a a script that strips out an obsolete header file (say “DM-Upload-Allowed”) across all Debian packages, we make the linter warn about the deprecated header and wait as all developers manually remove the deprecated header.

Silver Platter

Silver-platter is a new tool that aids in making automated changes across different version control repositories. It provides a common command-line interface and API that is not specific to a single version control system or hosting platform, so that it’s easy to propose changes based on a single script across a large set of repositories.

The tool will check out a repository, run a user-specified script that makes changes to the repository, and then either push those changes to the upstream repository or propose them for merging.

It’s specifically built so that it can be run in a shell loop over many different repository URLs.


As an example, you could use the following script ( to update the FSF address in copyright headers:


 perl -i -pe \
 'BEGIN{undef $/;} s/Free Software
 ([# ]+)Foundation, Inc\., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA/Free Software
 \1Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA/smg' *

 echo "Update FSF postal address."

Say you a wanted to create a merge proposal with these changes against offlineimap. First, log into GitHub (this needs to be done once per hosting site):

 $ svp login

To see what the changes would be without actually creating the pull request, do a dry-run:

 $ svp run --dry-run --diff ./
 Merge proposal created.
 Description: Update FSF postal address.

 === modified file ''
 --- upstream/ 2018-03-04 03:28:30 +0000
 +++ proposed/ 2019-04-06 21:07:25 +0000
 @@ -14,7 +14,7 @@
  #    You should have received a copy of the GNU General Public License
  #    along with this program; if not, write to the Free Software
 -#    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 +#    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

  import os
  import sys

 === modified file ''
 --- upstream/       2018-05-01 01:48:26 +0000
 +++ proposed/       2019-04-06 21:07:25 +0000
 @@ -19,7 +19,7 @@
  #    You should have received a copy of the GNU General Public License
  #    along with this program; if not, write to the Free Software
 -#    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 +#    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA

  import os
  from distutils.core import setup, Command

Then, create the actual pull request by running:

 $ svp run ./
 Reusing existing repository
 Merge proposal created.
 Description: Update FSF postal address.

This would create a new commit with the updated postal address (if any files were changed) and the commit message Update FSF postal address. You can see the resulting pull request here.

Debian-specific operations

To make working with Debian packaging repositories easier, Silver Platter comes with a wrapper (debian-svp) specifically for Debian packages.

This wrapper allows specifying package names to refer to packaging branches; packaging URLs are retrieved from the Vcs-Git header in a package. For example:

$ debian-svp run ~/ offlineimap

to fix the same issue in the offlineimap package.

(Of course, you wouldn’t normally fix upstream issues like this in the Debian package but forward them upstream instead)

There is also a debian-svp lintian-brush subcommand that will invoke lintian-brush on a packaging branch.

Supported technologies

Silver-Platter currently supports the following hosting platforms:

It works in one of three modes:

  • propose: Always create a pull request with the changes
  • push: Directly push changes back to the original branch
  • attempt-push: Attempt push, and fall back to propose if the current users doesn’t have permissions to push to the repository or the branch.


There is a Silver Platter repository on GitHub. Silver Platter is also available as a Debian package in unstable (not buster).

More information

For a full list of svp subcommands, see svp(1).


Breezy evolves

Last month Martin, Vincent and I finally released version 3.0.0 of Breezy, a little over a year after we originally forked Bazaar.

When we started working on Breezy, it was mostly as a way to keep Bazaar working going forward - in a world where Python 2 has mostly disappeared in favour of Python 3).


Since then, we have also made other improvements. In addition to Python 3 support, Breezy comes with the following other bigger changes:

Batteries Included

Breezy bundles most of the common plugins. This makes the installation of Breezy much simpler (pip install brz), and prevents possible issues with API incompatibility that plagued Bazaar.

Bundled plugins include: grep, git, fastimport, propose, upload, stats and parts of bzrtools.

>120 fixed bugs

Since Bazaar 2.7, lots of bugs in the Bazaar code base have been fixed (over 120 as of March 2019). We’ve also started an effort to go through all bugs in the Bazaar bug tracker to see whether they also apply to Breezy.

Native Git Support

Breezy now supports the Git file formats as a first class citizen; Git support is included in Breezy itself, and should work just as well as regular Bazaar format repositories.

Improved abstractions

Bazaar has always had a higher level API that could be used for version control operations, and which was implemented for both Bazaar, Git and Subversion formats.

As part of the work to support the Git format natively, we have changed the API to remove Bazaar-specific artefacts, like the use of file ids. Inventories (a Bazaar concept) are now also an implementation detail of the bzr formats, and not a concept that is visible in the API or UI.

In the future, I hope the API will be useful for tools that want to make automated changes to any version controlled resource, whether that be Git, Bazaar, Subversion or Mercurial repositories.


Lintian Brush

With Debian packages now widely being maintained in Git repositories, there has been an uptick in the number of bulk changes made to Debian packages. Several maintainers are running commands over many packages (e.g. all packages owned by a specific team) to fix common issues in packages.

Examples of changes being made include:

  • Updating the Vcs-Git and Vcs-Browser URLs after migrating from alioth to salsa
  • Stripping trailing whitespace in various control files
  • Updating e.g. homepage URLs to use https rather than http

Most of these can be fixed with simple sed or perl one-liners.

Some of these scripts are publically available, for example:


Lintian-Brush is both a simple wrapper around a set of these kinds of scripts and a repository for these scripts, with the goal of making it easy for any Debian maintainer to run them.

The lintian-brush command-line tool is a simple wrapper that runs a set of “fixer scripts”, and for each:

  • Reverts the changes made by the script if it failed with an error
  • Commits the changes to the VCS with an appropriate commit message
  • Adds a changelog entry (if desired)

The tool also provides some basic infrastructure for testing that these scripts do what they should, and e.g. don’t have unintended side-effects.

The idea is that it should be safe, quick and unobtrusive to run lintian-brush, and get it to opportunistically fix lintian issues and to leave the source tree alone when it can’t.


For example, running lintian-brush on the package talloc fixes two minor lintian issues:

 % debcheckout talloc
 declared git repository at
 git clone talloc ...
 Cloning into 'talloc'...
 remote: Enumerating objects: 2702, done.
 remote: Counting objects: 100% (2702/2702), done.
 remote: Compressing objects: 100% (996/996), done.
 remote: Total 2702 (delta 1627), reused 2601 (delta 1550)
 Receiving objects: 100% (2702/2702), 1.70 MiB | 565.00 KiB/s, done.
 Resolving deltas: 100% (1627/1627), done.
 % cd talloc
 talloc% lintian-brush
 Lintian tags fixed: {'insecure-copyright-format-uri', 'public-upstream-key-not-minimal'}
 % git log
 commit 0ea35f4bb76f6bca3132a9506189ef7531e5c680 (HEAD -> master)
 Author: Jelmer Vernooij <>
 Date:   Tue Dec 4 16:42:35 2018 +0000

     Re-export upstream signing key without extra signatures.

     Fixes lintian: public-upstream-key-not-minimal
     See for more details.

  debian/changelog                |   1 +
  debian/upstream/signing-key.asc | 102 +++++++++++++++---------------------------------------------------------------------------------------
  2 files changed, 16 insertions(+), 87 deletions(-)

 commit feebce3147df561aa51a385c53d8759b4520c67f
 Author: Jelmer Vernooij <>
 Date:   Tue Dec 4 16:42:28 2018 +0000

     Use secure copyright file specification URI.

     Fixes lintian: insecure-copyright-format-uri
     See for more details.

  debian/changelog | 3 +++
  debian/copyright | 2 +-
  2 files changed, 4 insertions(+), 1 deletion(-)

Script Interface

A fixer script is run in the root directory of a package, where it can make changes it deems necessary, and write a summary of what it’s done for the changelog (and commit message) to standard out.

If a fixer can not provide any improvements, it can simply leave the working tree untouched - lintian-brush will not create any commits for it or update the changelog. If it exits with a non-zero exit code, then it is assumed that it failed to run and it will be listed as such and its changes reset rather than committed.

In addition, tests can be added for fixers by providing various before and after source package trees, to verify that a fixer script makes the expected changes.

For more details, see the documentation on writing new fixers.


lintian-brush is currently available in unstable and testing. See man lintian-brush(1) for an explanation of the command-line options.

Fixer scripts are included that can fix (some of the instances of) 34 lintian tags.

Feedback would be great if you try lintian-brush - please file bugs in the BTS, or propose pull requests with new fixers on salsa.


Bazaar: A retrospective

For the last 7 years I’ve been involved in the Bazaar project. Since I am slowly stepping down, I recently wrote a retrospective on the project as I experienced it for the last 7 years.

Thanks to a few kind people for proofreading earlier drafts; if you spot any errors, please let me know in the comments.