fsck: improve committer/author check

fsck: improve committer/author check

fsck allows a name with > character in it like "name> <email>". Also for
"name email>" fsck says "missing space before email".

More precisely, it seeks for a first '<', checks that ' ' preceeds it.
Then seeks to '<' or '>' and checks that it is the '>'. Missing space is
reported if either '<' is not found or it's not preceeded with ' '.

Change it to following. Seek to '<' or '>', check that it is '<' and is
preceeded with ' '. Seek to '<' or '>' and check that it is '>'. So now
"name> <email>" is rejected as "bad name". More strict name check is the
only change in what is accepted.

Report 'missing space' only if '<' is found and is not preceeded with a
space.

Signed-off-by: Dmitry Ivankov <divanorama@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>