help: clarify the choice of pager

This follows the change made in d83e51654c8a to use environment variables
between system and user configuration.

mercurial/help/pager.txt

@@ -1,42 +1,43
 Some Mercurial commands can produce a lot of output, and Mercurial will
 attempt to use a pager to make those commands more pleasant.
 
 To set the pager that should be used, set the application variable::
 
   [pager]
   pager = less -FRX
 
-If no pager is set, Mercurial uses the environment variable
-$PAGER. If neither pager.pager, nor $PAGER is set, a default pager
-will be used, typically `less` on Unix and `more` on Windows.
+If no pager is set in the user or repository configuration, Mercurial uses the
+environment variable $PAGER. If $PAGER is not set, pager.pager from the default
+or system configuration is used. If none of these are set, a default pager will
+be used, typically `less` on Unix and `more` on Windows.
 
 .. container:: windows
 
   On Windows, `more` is not color aware, so using it effectively disables color.
   MSYS and Cygwin shells provide `less` as a pager, which can be configured to
   support ANSI color codes.  See :hg:`help config.color.pagermode` to configure
   the color mode when invoking a pager.
 
 You can disable the pager for certain commands by adding them to the
 pager.ignore list::
 
   [pager]
   ignore = version, help, update
 
 To ignore global commands like :hg:`version` or :hg:`help`, you have
 to specify them in your user configuration file.
 
 To control whether the pager is used at all for an individual command,
 you can use --pager=<value>:
 
   - use as needed: `auto`.
   - require the pager: `yes` or `on`.
   - suppress the pager: `no` or `off` (any unrecognized value
     will also work).
 
 To globally turn off all attempts to use a pager, set::
 
   [ui]
   paginate = never
 
 which will prevent the pager from running.