Is there a naming convention for git repositories?

lowercase-with-hyphens is the style I most often see on GitHub.*

lowercase_with_underscores is probably the second most popular style I see.

The former is my preference because it saves keystrokes.

^{* Anecdotal; I haven't collected any data.}

The problem with camel case is that there are often different interpretations of words - for example, checkinService vs checkInService. Going along with Aaron's answer, it is difficult with auto-completion if you have many similarly named repos to have to constantly check if the person who created the repo you care about used a certain breakdown of the upper and lower cases. avoid upper case.

His point about dashes is also well-advised.

1. use lower case.
2. use dashes.
3. be specific. you may find you have to differentiate between similar ideas later - ie use purchase-rest-service instead of service or rest-service.
4. be consistent. consider usage from the various GIT vendors - how do you want your repositories to be sorted/grouped?

I'd go for purchase-rest-service. Reasons:

1. What is "pur chase rests ervice"? Long, concatenated words are hard to understand. I know, I'm German. "Donaudampfschifffahrtskapitänspatentausfüllungsassistentenausschreibungsstellenbewerbung."

2. "_" is harder to type than "-"