Fix Windows os.popen bug with interleaved stdout/stderr output
See python bug 1366 "popen spawned process may not write to stdout under windows" for more details.
#!/bin/sh
# 0-2-4
# \ \ \
# 1-3-5
#
# rename in #1, content change in #4.
hg init t
cd t
touch 1
touch 2
hg commit -Am init -d "0 0" # 0
hg rename 1 1a
hg commit -m rename -d "0 0" # 1
hg co -C 0
echo unrelated >> 2
hg ci -m unrelated1 -d "0 0" # 2
hg merge --debug 1
hg ci -m merge1 -d "0 0" # 3
hg co -C 2
echo hello >> 1
hg ci -m unrelated2 -d "0 0" # 4
hg co -C 3
hg merge -y --debug 4
hg co -C 4
hg merge -y --debug 3