Use shutil.copystat in copyfile().
#!/bin/sh
# initial
hg init test-a
cd test-a
cat >test.txt <<"EOF"
1
2
3
EOF
hg add test.txt
hg commit -m "Initial" -d "1000000 0"
# clone
cd ..
hg clone test-a test-b
# change test-a
cd test-a
cat >test.txt <<"EOF"
one
two
three
EOF
hg commit -m "Numbers as words" -d "1000000 0"
# change test-b
cd ../test-b
cat >test.txt <<"EOF"
1
2.5
3
EOF
hg commit -m "2 -> 2.5" -d "1000000 0"
# now pull and merge from test-a
hg pull ../test-a
hg merge
# resolve conflict
cat >test.txt <<"EOF"
one
two-point-five
three
EOF
rm -f *.orig
hg resolve -m test.txt
hg commit -m "Merge 1" -d "1000000 0"
# change test-a again
cd ../test-a
cat >test.txt <<"EOF"
one
two-point-one
three
EOF
hg commit -m "two -> two-point-one" -d "1000000 0"
# pull and merge from test-a again
cd ../test-b
hg pull ../test-a
hg merge --debug
cat test.txt
hg debugindex .hg/store/data/test.txt.i
hg log