Currently, git-svn parses an authors file using the perl regex

/^(.+?|\(no author\))\s*=\s*(.+?)\s*<(.+)>\s*$/

in order to extract svn user name, real name and e-mail.
This does not match an empty e-mail field like "<>". On the other hand,
the output of an authors-prog is parsed with the perl regex

/^\s*(.+?)\s*<(.*)>\s*$/

in order to extract real name and e-mail.

So, specifying a trivial file grep such as

grep "$1" /tmp/authors | head -n 1 | cut -d'=' -f2 | cut -c'2-'

as the authors prog gives different results compared to specifying
/tmp/authors as the authors file directly.

Instead, make git svn uses the perl regex

/^(.+?|\(no author\))\s*=\s*(.+?)\s*<(.*)>\s*$/

for parsing the authors file so that the same (slightly more lenient)
regex is used in both cases.

Reported-by: Till Schäfer <till2.schaefer@tu-dortmund.de>
Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Eric Wong <normalperson@yhbt.net>