How to use git bisect
git bisect is a useful debugging tool. For context,
git bisect is a git command that can be used to track down the specific commit which a bug was introduced into the codebase.
If you can find a commit where the code works properly and a commit with the offending bug, you don’t have to trace down the buggy commit by hand. The
git bisect command, via binary search, will help you find the offending commit. For example, the Git documentation has a handy
git bisect guide that shows two ways to use it.
How to git bisect in projects using Bundler
A few things that may not be obvious are needed for
git bisect to work
in a project that uses Bundler.
Gemfile.lockneeds to be in the git repo, so that each commit will load the same dependencies every time.
- Each step during the bisect needs to run
bundle installfirst, so that the correct dependencies are installed and available to be loaded.
- After determining if the commit is good or bad, each step needs to
git reset. If
bundle installor running the test can cause changes on the file system, which would prevent
git checkoutof the next commit to test if they are not reset.
Here’s a minimal example script that runs the rake task
#!/usr/bin/env bash bundle install bin/rake spec status=$? git reset --hard HEAD exit $status
See also the discussion at bundler/bundler#3726.