Gettext Umbrella Issue

Minimum example to reproduce a bug

Issue: elixir-gettext/gettext#178
My current workaround: https://gist.github.com/amatalai/1877f48a195f578682cfd20e66c6544e

Additional info

• app C depends on app B
• app B depends on app A
• app A is empty
• app B contains module B.Gettext with use Gettext
• app C contains module C which imports B.Gettext and calls single dgettext macro

Steps to reproduce

1. Run mix gettext.extract from umbrella root. It creates apps/b/priv/gettext/c.pot file with msgid "String C". Everything is ok for now.
2. Run mix gettext.extract second time. msgid "String C" is removed from c.pot.