git-svn: Same default as cvsimport when using --use-log-author

git-svn: Same default as cvsimport when using --use-log-author

When using git-cvsimport, the author is inferred from the cvs commit,
e.g. cvs commit logname is foobaruser, then the author field in git
results in:

Author: foobaruser <foobaruser>

Which is not perfect, but perfectly acceptable given the circumstances.

The default git-svn import however, results in:

Author: foobaruser <foobaruser@acf43c95-373e-0410-b603-e72c3f656dc1>

When using mixes of imports, from CVS and SVN into the same git
repository, you'd like to harmonise the imports to the format cvsimport
uses.
git-svn supports an experimental option --use-log-author which currently
results in the same logentry as without that option when no From: or
Signed-off-by: is found in the logentry ($email currently ends up empty,
and hence is generated again).

This patches harmonises the result with cvsimport, and makes
git-svn --use-log-author produce:

Author: foobaruser <foobaruser>

Signed-off-by: Stephen R. van den Berg <srb@cuci.nl>
Acked-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>