Sheldon behaviour with submodules

Summary

When trying to pass Sheldon on 2 commits after a merge on a repository with submodules, there is strange messages that makes most of CI jobs failing on application repositories.

Steps to reproduce

• Cloning a repository containing submodules
• Try to execute sheldon between two commit with one containing a submodule update
• Sheldon shouldn't pass

Dev environment

• Commit: dev

What is the current bug behavior?

Sheldon doesn't succeed to execute when there is submodule updates in commits.

What is the expected correct behavior?

Sheldon shouldn't parse submodules or at least should success to do it.

Possible fixes