When uploading a new library package which changes its API/behavior in a subtle way, typically you will only hear about the downstream breakage after you’ve uploaded the new library package (via bug reports telling you that your package FTBFS, fails to build from source).

I prefer quality-assurance to happen proactively rather than reactively whenever possible, so I set out to write a tool which automates the rebuild of reverse-build-dependencies, i.e. all packages whose build process could be affected by the package one is about to upload.

The result is a tool called ratt, which is short for “Rebuild All The Things!”. It injects the newly-built Debian package you provide it, figures out all the reverse-build-dependencies, invokes sbuild for all of them, and finally presents you with a list of packages that failed to build.

To demonstrate how the tool works, let’s assume we want to upload a new version of the Go library github.com/jacobsa/gcloud. To keep this example brief, we don’t actually do anything to the package but bump its version number:

midna /tmp $ debcheckout golang-github-jacobsa-gcloud-dev
declared git repository at git://anonscm.debian.org/pkg-go/packages/golang-github-jacobsa-gcloud.git
git clone git://anonscm.debian.org/pkg-go/packages/golang-github-jacobsa-gcloud.git golang-github-jacobsa-gcloud-dev ...
Cloning into 'golang-github-jacobsa-gcloud-dev'...
remote: Counting objects: 84, done.
remote: Compressing objects: 100% (73/73), done.
remote: Total 84 (delta 19), reused 0 (delta 0)
Receiving objects: 100% (84/84), 87.70 KiB | 0 bytes/s, done.
Resolving deltas: 100% (19/19), done.
Checking connectivity... done.
midna /tmp $ cd golang-github-jacobsa-gcloud-dev
midna /tmp/golang-github-jacobsa-gcloud-dev $ dch -i -m 'dummy new version'
midna /tmp/golang-github-jacobsa-gcloud-dev $ git commit -a -m 'dummy new version'
midna /tmp/golang-github-jacobsa-gcloud-dev $ gbp buildpackage --git-pbuilder
[…]

So far, so good. Now let’s invoke ratt to rebuild all reverse-build-dependencies:

midna /tmp/golang-github-jacobsa-gcloud-dev $ ratt golang-github-jacobsa-gcloud_0.0\~git20150709-2_amd64.changes         
2015/08/16 11:48:41 Loading changes file "golang-github-jacobsa-gcloud_0.0~git20150709-2_amd64.changes"
2015/08/16 11:48:41  - 1 binary packages: golang-github-jacobsa-gcloud-dev
2015/08/16 11:48:41  - corresponding .debs (will be injected when building):
2015/08/16 11:48:41     golang-github-jacobsa-gcloud-dev_0.0~git20150709-2_all.deb
2015/08/16 11:48:41 Loading sources index "/var/lib/apt/lists/ftp.ch.debian.org_debian_dists_sid_contrib_source_Sources"
2015/08/16 11:48:41 Loading sources index "/var/lib/apt/lists/ftp.ch.debian.org_debian_dists_sid_main_source_Sources"
2015/08/16 11:48:43 Loading sources index "/var/lib/apt/lists/ftp.ch.debian.org_debian_dists_sid_non-free_source_Sources"
2015/08/16 11:48:43 Building golang-github-jacobsa-ratelimit_0.0~git20150723.0.2ca5e0c-1 (commandline: [sbuild --arch-all --dist=sid --nolog golang-github-jacobsa-ratelimit_0.0~git20150723.0.2ca5e0c-1 --extra-package=golang-github-jacobsa-gcloud-dev_0.0~git20150709-2_all.deb])
2015/08/16 11:49:19 Build results:
2015/08/16 11:49:19 PASSED: golang-github-jacobsa-ratelimit_0.0~git20150723.0.2ca5e0c-1

Thanks for reading this far, and I hope ratt makes your life a tiny bit easier. As ratt just entered Debian unstable, you can install it using apt-get install ratt. If you have any feedback, I’m eager to hear it.