Dominic Cleal's Blog

Mon, 07 Apr 2014 08:22:00 BST

permalink Reproducible builds on Copr with tito and git-annex

Recently, Fedora's Copr service was launched which lets individuals create personal repos and build packages on Fedora's servers for a number of Fedora and EL versions (similar to OBS and PPAs).

I've set up a couple of repos under it, and one which contains builds of various gems as dependencies for librarian-puppet. Setting up and tracking RPM builds is made quite easy with git and tito, which lets you set up a simple directory structure in your RPM repo, track specs and source binaries (.gem files), tag and release changes to Copr:

$ tree 
.
|-- README.md
|-- rel-eng
|   |-- packages
|   |   |-- rubygem-highline
|   |   |-- rubygem-librarian
|   |   |-- rubygem-librarian-puppet
|   |   `-- rubygem-thor
|   |-- releasers.conf
|   `-- tito.props
|-- rubygem-highline
|   |-- highline-1.6.20.gem
|   `-- rubygem-highline.spec
|-- rubygem-librarian
|   |-- librarian-0.1.2.gem
|   `-- rubygem-librarian.spec
|-- rubygem-librarian-puppet
|   |-- librarian-puppet-0.9.17.gem
|   `-- rubygem-librarian-puppet.spec
|-- rubygem-thor
|   |-- rubygem-thor.spec
|   `-- thor-0.15.4.gem
`-- setup_sources.sh

6 directories, 16 files

(my librarian-puppet-copr repo)

However storing binary files in git has lots of problems, including the resulting size of the repo. To solve this, I use git-annex so the repo only stores metadata and a local cache of the binaries. The binaries can then be fetched from the web on a clean checkout using the setup_sources.sh script and git-annex on the fly.

Setting this up is easy:

  1. mkdir myrepo && cd myrepo
  2. git init
  3. git annex init
  4. tito init
Next, configure Copr and tito to use Copr using Mirek Suchý's blog post and my rel-eng directory. The key part of the rel-eng configuration for using the git-annex support in tito 0.5.0 is setting the builder in tito.props:

[buildconfig]
builder = tito.builder.GitAnnexBuilder

Adding new packages is now a matter of doing:

  1. mkdir rubygem-foo && cd rubygem-foo
  2. vim rubygem-foo.spec
  3. git annex addurl --file=foo-1.2.3.gem http://rubygems.org/downloads/foo-1.2.3.gem or copy the file into place and run git annex add foo-1.2.3.gem
  4. git commit -am "Add foo 1.2.3"
  5. tito tag --keep-version
  6. tito release copr-domcleal

git-annex will store the file in its local storage under .git/annex, replacing the file in git with a symlink based on the checksum of the contents. When you push the repo to a remote without git-annex support (like GitHub), then the binaries won't be transferred, keeping the size small. Other users can fetch binaries by adding a shared remote (e.g. a WebDAV or rsync share or web remotes using setup_sources.sh).

When tito is building SRPMs, it will "unlock" the files, fetching them from available remotes, build the RPM and then re-lock the checkout.

So the combination of git (for tracking sources and specs), git-annex (for keeping sources outside git), tito (for tagging builds) and Copr (for building and publishing) makes it easy to build and release your own RPMs, while allowing you to make the source code and build process accessible and transparent.

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