help: properly document the default pattern

The default isn't to glob. It's relpath, which does no globbing at
all. Thus most commands and options like -X/-I and hg files require
`glob:` in front of them to actually do any globbing.

I think long ago the default was to glob, but that hasn't been true
for a long time.

mercurial/helptext/patterns.txt

@@ -1,8 +1,10 b''
 Mercurial accepts several notations for identifying one or more files
 at a time.
 
-By default, Mercurial treats filenames as shell-style extended glob
-patterns.
+By default, Mercurial treats filenames verbatim without pattern
+matching, relative to the current working directory. Note that your
+system shell might perform pattern matching of its own before passing
+filenames into Mercurial.
 
 Alternate pattern notations must be specified explicitly.