Return just the x-commit SHA and subject in gen
Return just the x-commit SHA and subject in gen

In git v2.2.1 the command 'git show --oneline HEAD' includes the diff in addition to the
SHA and the commit subject. This breaks the generate command, as it expects a single line
of output.

robphoenix/exercism-go,exercism/xgo,leenipper/xgo,robphoenix/exercism-go,leenipper/xgo,exercism/xgo