mq: new commands qselect, qguard
implement quilt-style guards for mq.
guards allow to control whether patch can be pushed.
if guard X is active and patch is guarded by +X (called "posative guard"),
patch can be pushed. if patch is guarded by -X (called "nagative guard"),
patch cannot be pushed and is skipped.
use qguard to set/list guards on patches. use qselect to set/list
active guards.
also "qseries -v" prints guarded patches with "G" now.
adding a
adding b
adding t.h
adding t/x
a
NONEXISTENT: No such file or directory
a
b
t.h
t/x
a: No such file or directory
NONEXISTENT: No such file or directory
b
t.h
t/x
a
NONEXISTENT: No such file in rev ce18e5bc5cd3
a
t/x
b
t.h
% -I/-X with relative path should work
b
t.h
t/x
t/x
t/x