Also find correct column width of wide characters.
Use unicodedata.east_asian_width() to determine wide/full width
characters if available. Otherwise, return character count as before.
#!/bin/sh
hg init repo
cd repo
echo line 1 > foo
hg ci -qAm 'add foo' -d "1000000 0"
# copy foo to bar and change both files
hg cp foo bar
echo line 2-1 >> foo
echo line 2-2 >> bar
hg ci -m 'cp foo bar; change both' -d "1000000 0"
# in another branch, change foo in a way that doesn't conflict with
# the other changes
hg up -qC 0
echo line 0 > foo
hg cat foo >> foo
hg ci -m 'change foo' -d "1000000 0"
# we get conflicts that shouldn't be there
hg merge --debug
echo "-- foo --"
cat foo
echo "-- bar --"
cat bar