During deploy, skip bundle install when Gemfile.lock has not changed

[martinemde]

Use the same utility that assets checking is using to determine code changes and only re-bundle when something has changed. Probably want to check vendored gems too.

[tmiller]

I understand that bundler has gotten more intelligent about when it downloads gems, and I checked a deploy log and my bundle command ran within a second since the Gemfile.lock did not change. Is this still something you still want to pursue?

[martinemde]

I think you're right. According to the changelog in bundler we should be able to speed up installs significantly without doing anything fancy. I'll leave this ticket on hold until we can see how bundler 1.5.0 does and if it solves the slow install issues enough for most people.