Add 'git svn help [cmd]' which works outside a repo.
Add 'git svn help [cmd]' which works outside a repo.

Previously there was no explicit 'help' command, but 'git svn help'
still printed the usage message (as an invalid command), provided you
got past the initialization steps that required a valid repo.

Signed-off-by: Ben Jackson <73675debcd8a436be48ec22211dcf44fe0df0a64@ben.com>
Acked-by: Eric Wong <8c2951295f8292b0c03727bc4652981172298eae@yhbt.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git