Fix crash when updating git dependencies

[deivid-rodriguez]

If there's an evaled gemfile that also includes git dependencies, it would result in a crash like the following:

Failure/Error:
  dependency.requirements.
  find { |f| f[:file] == file.name }.
  fetch(:source).fetch(:ref)

NoMethodError:
  undefined method `fetch' for nil:NilClass

              fetch(:source).fetch(:ref)

We need to check the Gemfile name being updated, not generic names when figuring out if we should update any git pins.