Git pull/checkout/clone fails on Windows

Attempting to integrate this into CMake with the ExternalProject module. Git pull fails with various errors on Windows only; files (pretty much tests) include characters that give "invalid argument" errors (mainly colons and other characters disallowed by Windows in filenames). Is there a way this can either be fixed or ignored? As a result of this, git fails with the following error when pulling:
```
fatal: Could not reset index file to revision 'HEAD'.
Cannot rebase: You have unstaged changes.
Please commit or stash them.
No rebase in progress?
```