On Unix systems, line endings are represented by linefeeds (LF). In windows, a string is represented by a carriage return (CR) and a line feed (LF), thus (CRLF). when you get the code from git that was downloaded from the Unix system, they will only have LF.
If you want to disable this warning, enter it at the git command line
git config core.autocrlf true
If you want to make a smart decision how Git should handle this, read the documentation
Here is a snippet
Formatting and spaces
Formatting and space issues are some of the most annoying and subtle issues that many developers face when working together, especially cross-platform ones. For patches or other collaboration, it’s very easy to make small whitespace changes because editors silently present them, and if your files ever touch the Windows system, their line endings may be replaced. Git has several configuration options to help with these problems.
core.autocrlf
If you program on Windows and work with people who aren't (or vice versa), you are likely to run into problems with line endings at some point. This is because Windows uses both a carriage return and a line feed for newlines in its files, while Mac and Linux systems use only a line feed. This is a subtle but incredibly annoying fact of cross-platform work; many Windows editors silently replace existing LF-style line endings with CRLF, or insert both end-of-line characters when the user presses the enter key.
Git can handle this by automatically converting CRLF line endings to LF when you add a file to the index, and vice versa, when it checks the code on your file system. You can enable this function using the core.autocrlf parameter. If you are on a Windows computer, set it to true - this will convert LF endings to CRLF when checking the code:
$ git config --global core.autocrlf true
If you are running a Linux or Mac system that uses LF line endings, you do not want Git to automatically convert them when you extract files; however, if a file with CRLF endings is accidentally inserted, you might want Git to fix it. You can tell Git to convert CRLF to LF when committed, but not vice versa by setting core.autocrlf to input:
$ git config --global core.autocrlf input
This setting should leave you with CRLF endings in Windows checks, but with LF endings on Mac and Linux systems and in the repository.
If you are a Windows programmer who runs a project for Windows only, you can disable this function by writing the carriage return to the repository, setting the configuration parameter to false:
$ git config --global core.autocrlf false