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
# test dirstate._dirs refcounting
hg init t
cd t
mkdir -p a/b/c/d
touch a/b/c/d/x
touch a/b/c/d/y
touch a/b/c/d/z
hg ci -Am m
hg mv a z