bk pmerge : add new markers, fix a i/o bug bring back the test script for pmerge.
bk pmerge : add new markers, fix a i/o bug
bring back the test script for pmerge.

bk: 39f7b2d6_UieT448F6VM5lO-s9Nlcg
bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper,bitkeeper-scm/bitkeeper