ref-filter: truncate atom names in error messages

If you pass a bogus argument to %(refname), you may end up with a message like this: $ git for-each-ref --format='%(refname:foo)' fatal: unrecognized %(refname:foo) argument: foo which is confusing. It should just say: fatal: unrecognized %(refname) argument: foo which is clearer, and is consistent with most other atom parsers. Those other parsers do not have the same problem because they pass the atom name from a string literal in the parser function. But because the parser for %(refname) also handles %(upstream) and %(push), it instead uses atom->name, which includes the arguments. The oid atom parser which handles %(tree), %(parent), etc suffers from the same problem. It seems like the cleanest fix would be for atom->name to be _just_ the name, since there's already a separate "args" field. But since that field is also used for other things, we can't change it easily (e.g., it's how we find things in the used_atoms array, and clearly %(refname) and %(refname:short) are not the same thing). Instead, we'll teach our error_bad_arg() function to stop at the first ":". This is a little hacky, as we're effectively re-parsing the name, but the format is simple enough to do this as a one-liner, and this localizes the change to the error-reporting code. We'll give the same treatment to err_no_arg(). None of its callers use this atom->name trick, but it's worth future-proofing it while we're here. Signed-off-by: Jeff King <peff@peff.net> Acked-by: Taylor Blau <me@ttaylorr.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>