Documentation and returned error should declare naming conventions

[itaiad200]

I got from the server on create branch: argument branchID: invalid value: validation error
It took me a lot of time to figure out that the branch name must match ^\w[-\w]*$ , and in one of our configurations the branch name contained . .
Btw I didn’t find such restriction in documentation, but anyway, if the returned error message will provide any info/hint about the error it would safe a lot of investigation time