Add support for .gitignore pattern negation
Created originally on Bitbucket by wberrier (Wade Berrier)
See for reference: https://git-scm.com/docs/gitignore
If a pattern starts with !, it negates that pattern.
The repo clones just fine, but when running status, this error message comes up:
.gitignore: unsupported ignore pattern '!.gitignore'
Here's a sample repo that uses these types of ignore files: