Font files not valid when syncing with git on Windows

On Windows 10 (with Cygwin (64-bit))
1. `git clone https://github.com/google/fonts.git google_fonts.git`
2. In File Explorer, open a ttf file in `google_fonts.git`
3. Windows Font Viewer displays "The requested file [...].ttf is not a valid font file."

```
$ git --version
git version 2.8.3

$ git config --list
core.autocrlf=true
core.repositoryformatversion=0
core.filemode=true
core.bare=false
core.logallrefupdates=true
core.ignorecase=true
remote.origin.url=https://github.com/google/fonts.git
remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
branch.master.remote=origin
branch.master.merge=refs/heads/master
```