Error dialog "File" excludes "does not exist" when creating a new project git -backed Xcode

When creating a new project in XCode 6, if I checked the "Source: Generate Git on My Mac" button on the Save page, the project is successfully created, but I get a dialog box with the message

The "exclude" file does not exist

Also, the Git repo is initialized for this project, but no files are added to it.

Why is this happening and how can I fix it?

(Visible on Yosemite, in several versions of XCode 6, including both 6.0.x and 6.1.x).