run merge program in repo root.
before, merge program was run in user current directory. Well defined
location is better for scripts. no more need to pass HG_ROOT to merge
program now.
%% should show b unknown
? b
%% should show b unknown and c modified
M c
? b
%% should show b added and c modified
M c
A b
%% should show a removed, b added and c modified
M c
A b
R a
%% should show b added and c modified
M c
A b
%% should show b unknown and c modified
M c
? b
%% should show b unknown
? b
%% should show a b and c
a
b
c