pass-the-fork — inject forked dependencies into CI builds

When making changes to several related repositories, by default CI tests each against unmodified dependencies. This tool will allow explicitly requesting a testing against modified dependencies.

Currently working on injecting Ruby gems into Travis builds, for GitHub pull requests. I'd love to expand each of these (details below).

Use cases

Imagine repository X is a library on which repository Y depends.

1. Compatibility: @you forked X, sent pull request X#1, wonder if it'll break Y. By default Y tests weren't even run. Want to run B tests against you/X fork at your-x-branch-1.

2. Dependent PRs: you forked both, sent pull requests X#2 which adds new api, Y#2 which uses it. By default, Y#2 is tested against X@master and obviously fails. Want to run you/Y@your-y-branch-2 fork tests against you/X@your-x-branch-2 fork.

3. ...

[TODO: flesh this out, add diagram, include merge order considerations...]

Functionality (nothing working yet, but this shows what I'm starting from)

The long-term goal is to help test/coordinate/present related changes accross all kinds of free / open source software, that were not necessarily aware of each other.

• translate PR urls to specific git url & branch (or commit).

  • WIP GitHub pull request url
  • GitLab pull request url
  • other hosts...
  • any hg/bzr/svn/etc branch?
  • patch in mailing list / issue trackers?

• WIP script to override one or more dependencies

  • WIP Ruby gems
  • Javascript npm packages
  • ...

  far off future: would love to do not only source package managers but also:

  • git submodules
  • vendored code
  • docker images
  • build-time shell install commands like apt/rpm, tarballs, ...
  • run-time fetching dependencies (eg. javascript from CDNs)

• WIP CLI to trigger CI run with above overriding script

  • WIP on Travis via https://docs.travis-ci.com/user/triggering-builds API (using trigger-travis)
  • ...

• Report build status back on pull request.

  • GitHub status API apparently requires repo write permissions :-(
  • badge image?
  • make textual comment on PR?
    • on update, remove previous comment (like miq_bot does for linter comments)

• A way to re-run on PR changes. (For starters, just re-run the CLI)

• A bot that does the above? For now I'd like to get as far as possible without bots, only CLI anybody can run...

• Record versions actually used in a build? (feels a good idea, but what's the use case? possibly belongs in separate project.)

Prior art

• Trigger a Travis CI build from another project’s build, Ramesh Nair, https://github.com/waigo/waigo/blob/master/scripts/triggerDocSiteBuild.js
• https://stackoverflow.com/a/34273424/239657, Michael Ernst, https://github.com/mernst/plume-lib/blob/master/bin/trigger-travis.sh
• https://github.com/stephanmg/travis-dependent-builds, Stephan Grein
• [http://eng.rightscale.com/2015/04/27/dependent-builds-in-travis.html](Dependent builds in Travis), Sean McGivern — obsolete, was restarting builds before trigger new build was possible.
• Improving hosted continuous integration services, Christopher Weyand, Jonas Chromik, Lennard Wolf, Steffen Kötte, Konstantin Haase, Tim Felgentreff, Jens Lincke, Robert Hirschfeld