tests/test-locate.out

make hook code nicer.
pre hooks can raise exception if fail.
tidy up better if exception raised (like KeyboardInterrupt) when running
hook program.

adding a
adding b
a
NONEXISTENT: No such file or directory
a
b
a: No such file or directory
NONEXISTENT: No such file or directory
b
a
NONEXISTENT: No such file in rev 9e1684505872
a
b