util.copyfiles: only switch to copy if hardlink raises IOError or OSError.
before this, interrupting clone would give "file a same as file b" error
because caught KeyboardInterrupt.
syntax: glob
*.elc
*.orig
*.rej
*~
*.so
*.pyc
*.swp
*.prof
tests/*.err
build
dist
doc/*.[0-9]
doc/*.[0-9].gendoc.txt
doc/*.[0-9].{x,ht}ml
MANIFEST
patches
mercurial/__version__.py
syntax: regexp
^\.pc/