Add --dry-run flag to clean

[wfarr]

Prints out gems instead of removing them.

[wfarr]

/cc #2236

[ghost]

The --dry-run output should be identical as though the command was actually run IMO. So it should be something like:

  Bundler.ui.info "Removing #{output}"

  unless Bundler.settings[:dry_run]
    FileUtils.rm_rf(gem_dir)
  end
end

Also while running through the stale_gem_files, stale_gemspec_files and stale_git_cache_dirs you don't need to add a check for dry run setting. You can just surround the existing code in an if/unless block like so:

unless Bundler.settings[:dry_run]
  stale_gem_files.each {|file| FileUtils.rm(file) if File.exists?(file) }
  stale_gemspec_files.each {|file| FileUtils.rm(file) if File.exists?(file) }
  stale_git_cache_dirs.each {|dir| FileUtils.rm_rf(dir) if File.exists?(dir) }
end

What do you think?

[wfarr]

@Rohit I'm 👍 on DRYing things up a bit with just wrapping all the iterators in the check. I do think there's merit in making the output sufficiently different for a dry run though.

[wfarr]

Also, the failed CI status there looks to have been one of the Travis VMs failing on some SSH key related thing. Triggering another build should make it go green.

[wfarr]

All right, CI is green and the code has been DRYed up a bit.

[ghost]

@indirect can you take a look at this PR? :)

[indirect]

I think the way clean works could use some refactoring, but that's outside the scope of this pull. :) Looks good, thanks @wfarr!

[guyisra]

anyone knows why heroku uses dry-run ON as default? it seems ever since this pull was introduced no gems are being deleted...