rebase: do not print lots of usage hints after an obvious error message

When a non-existent branch was specified to be rebased, the complete usage information is printed after the error message that carries the relevant piece of information: $ git rebase master topci fatal: no such branch: topci usage: git rebase [-i] [options] [--onto <newbase>] [<upstream>] [<branch>] or: git rebase [-i] [options] --onto <newbase> --root [<branch>] or: git-rebase [-i] --continue | --abort | --skip Available options are [30 lines of usage stripped] The error message was introduced recently by 4ac5356c (rebase: give a better error message for bogus branch, 2011-01-27), and the result was acceptable because the usage text was just two lines. But 45e2acf3 (rebase: define options in OPTIONS_SPEC, 2011-02-28) made things worse because the usage text is now 35 lines. Just drop the usage information because it does not add value to the error message. Signed-off-by: Johannes Sixt <j6t@kdbg.org> Acked-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>