new extension: fetch -> combine pull and merge/update
pull changes from remote repo.
if changes add new head: merge with new head, commit result.
else: update working dir to new head.
this makes useful command like git 'pull' command.
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