[PATCH 2 of 3 STABLE V2] pager: document the 'ui.pager' option

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at ens-lyon.org>
# Date 1493649823 -7200
#      Mon May 01 16:43:43 2017 +0200
# Branch stable
# Node ID e8dd07d6bb6dedaf466ed29e8de0789e8a8f1076
# Parent  853bf9ca7b3b1f4d8f54ed8c60ff92371132c097
# EXP-Topic pager
# Available At https://www.mercurial-scm.org/repo/users/marmoute/mercurial/
#              hg pull https://www.mercurial-scm.org/repo/users/marmoute/mercurial/ -r e8dd07d6bb6d
pager: document the 'ui.pager' option

The 'config' helps was missing help about pager enabling/disabling.

diff --git a/mercurial/help/config.txt b/mercurial/help/config.txt
--- a/mercurial/help/config.txt
+++ b/mercurial/help/config.txt
@@ -1960,6 +1960,10 @@ User interface controls.
     The path to a directory used to store generated .orig files. If the path is
     not a directory, one will be created.
 
+``pager``
+  Control the pagination of command output (default: True). See :hg:`help pager`
+  for details.
+
 ``patch``
     An optional external tool that ``hg import`` and some extensions
     will use for applying patches. By default Mercurial uses an