git p4: implement view spec wildcards with "p4 where"

git p4: implement view spec wildcards with "p4 where"

"git p4" does not support many of the view wildcards, such as * and
%%n.  It only knows the common ... mapping, and exclusions.

Redo the entire wildcard code around the idea of directly querying
the p4 server for the mapping.  For each commit, invoke "p4 where"
with committed file paths as args and use the client mapping to
decide where the file goes in git.

This simplifies a lot of code, and adds support for all wildcards
supported by p4.  Downside is that there is probably a 20%-ish
slowdown with this approach.

[pw: redo code and tests]

Signed-off-by: Kazuki Saitoh <ksaitoh560@gmail.com>
Signed-off-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>