avoid calling (cd ...) with `nil' as a directory name
When (hg-root) cannot determine the current Mercurial root, print an
error message instead of trying to evaluate (cd nil).
syntax: glob
*.elc
*.orig
*.rej
*~
*.o
*.so
*.pyc
*.swp
*.prof
tests/.coverage*
tests/annotated
tests/*.err
build
contrib/hgsh/hgsh
dist
doc/*.[0-9]
doc/*.[0-9].gendoc.txt
doc/*.[0-9].{x,ht}ml
MANIFEST
patches
mercurial/__version__.py
syntax: regexp
^\.pc/
Output/Mercurial-[0-9.]*.exe