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.

+ mkdir t
+ cd t
+ hg init
+ echo a
+ hg add a
+ hg commit -m test -d '0 0'
+ hg history
changeset:   0:acb14030fe0a
tag:         tip
user:        test
date:        Thu Jan  1 00:00:00 1970
summary:     test

+ hg manifest
b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3 644 a
+ hg cat a
a
+ hg verify
checking changesets
checking manifests
crosschecking files in changesets and manifests
checking files
1 files, 1 changesets, 1 total revisions