Reduce the amount of stat traffic generated by a walk. When we switched to the new walk code for commands, we no longer passed a list of specific files to the repo or dirstate walk or changes methods. This meant that we always walked and attempted to match everything, which was not efficient. Now, if we are given any patterns to match, or nothing at all, we still walk everything. But if we are given only file names that contain no glob characters, we only walk those.

pulling from ../a
searching for changes
warning: pulling from an unrelated repository!
adding changesets
adding manifests
adding file changes
added 1 changesets with 1 changes to 1 files
(run 'hg update' to get a working copy)
changeset:   1:9a79c33a9db3
tag:         tip
user:        a
date:        Thu Jan  1 00:00:00 1970
summary:     a

changeset:   0:01f8062b2de5
user:        b
date:        Thu Jan  1 00:00:00 1970
summary:     b