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.
unknown
acb14030fe0a tip
acb14030fe0a21b60322c440ad2d20cf7685a376 first
tip 1:b9154636be938d3d431e75a7c906504a079bfe07
first 0:acb14030fe0a21b60322c440ad2d20cf7685a376
b9154636be93 tip
M a
b9154636be93+ tip
acb14030fe0a+ first
acb14030fe0a21b60322c440ad2d20cf7685a376+ first
M a
c8edf04160c7 tip
c8edf04160c7+b9154636be93+ tip
M .hgtags