blame: tolerate bogus e-mail addresses a bit better

blame: tolerate bogus e-mail addresses a bit better

The names and e-mails are sanitized by fmt_ident() when creating commits,
so that they do not contain "<" nor ">", and the "committer" and "author"
lines in the commit object will always be in the form:

    ("author" | "committer") name SP "<" email ">" SP timestamp SP zone

When parsing the email part out, the current code looks for SP starting
from the end of the email part, but the author could obfuscate the address
as "author at example dot com".

We should instead look for SP followed by "<", to match the logic of the
side that formats these lines.

Signed-off-by: Josh Stone <jistone@redhat.com>
Reviewed-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>