To use overcommit, it will copy some files (namely template-dir/hooks/*) into the .git/hooks directory of a git repo where you want to install it. The problem is that the gem overcommit is required in these scripts (via require 'overcommit) but can't be found. I have no idea how to fix this. Updating the LOAD_PATH in gemset-config doesn't work..

Does anyone have an idea?

The problem is that ruby needs to be installed along with overcommit to get this working. How can I tell nix to do so?

The problem is that ruby needs to be installed along with overcommit to get this working. How can I tell nix to do so?

The way to fix this is to make the overcommit hook a wrapper that sets the RubyGems environment variables, and then loads the real hook.

Now, doing this is easier said than done, and it’s taken me a whole evening to figure out how to, because I don’t think we’ve ever had a situation like this before, but I have it working now.

Do you mind if I just push a commit to your branch?

Oh great, yes feel free to push your changes!

It does not work for me..

1. I checked out the branch.
2. Executed nix run -f . gitAndTools.overcommit mdl ruby.
3. Created minimal config:

verify_signatures: false

PreCommit:
  Mdl:
    enabled: true

4. Executed overcommit --install
5. Staged a change in a Markdown file.
6. Then tried to commit, resulting in this:

This repository contains hooks installed by Overcommit, but the `overcommit` gem is not installed.
Install it with `gem install overcommit`.

Furthermore, if I understand your changes correctly, the hooks aren't wrapped:

$> head -n20 .git/hooks/pre-commit
#!/nix/store/k6bmp8wix8f350nwkrmcybx3b7yfbcam-ruby-2.5.3/bin/ruby

# Entrypoint for Overcommit hook integration. Installing Overcommit will result
# in all of your git hooks being copied from this file, allowing the framework
# to manage your hooks for you.

# Prevent a Ruby stack trace from appearing when we interrupt the hook.
# Note that this will be overridden when Overcommit is loaded, since the
# InterruptHandler will redefine the trap at that time.
Signal.trap('INT') do
  puts 'Hook run interrupted'
  exit 130
end

# Allow hooks to be disabled via environment variable so git commands can be run
# in scripts without Overcommit running hooks
if ENV['OVERCOMMIT_DISABLE'].to_i != 0 || ENV['OVERCOMMIT_DISABLED'].to_i != 0
  exit
end

@alyssais Are you still interested in giving your input? Otherwise I will close this PR because I am unable to fix this.

As I'm not able to fix this, I'm closing this PR. If anyone wants to reopen and fix it, feel free to do so.