[PATCH 1 of 2 STABLE V2 STABLE] sparserevlog: document the config option

[Boris Feld]

# HG changeset patch
# User Boris Feld <boris.feld at octobus.net>
# Date 1548868538 -3600
#      Wed Jan 30 18:15:38 2019 +0100
# Branch stable
# Node ID cf5421ca2bea707ce52fc96f5ca68cf8f4894e8c
# Parent  ab0d762d89ef6e2fdcf2a4cc31e9889ea04bc13b
# EXP-Topic issue6056
# Available At https://bitbucket.org/octobus/mercurial-devel/
#              hg pull https://bitbucket.org/octobus/mercurial-devel/ -r cf5421ca2bea
sparserevlog: document the config option

This was overlooked when this graduated from experimental.

diff --git a/mercurial/help/config.txt b/mercurial/help/config.txt
--- a/mercurial/help/config.txt
+++ b/mercurial/help/config.txt
@@ -857,6 +857,16 @@ https://www.mercurial-scm.org/wiki/Missi
 
     Enabled by default.
 
+``sparse-revlog``
+    Enable of disable the ``sparse-revlog`` delta strategy. This format improves
+    delta re-use inside revlog. For very branchy repostiories, it result in a
+    smaller store. For repositories with many revisions it also help performance
+    (by using shorted delta chains)
+
+    Repositories with this on-disk format require Mercurial version 4.7
+
+    Enabled by default.
+
 ``graph``
 ---------
 
diff --git a/tests/test-help.t b/tests/test-help.t
--- a/tests/test-help.t
+++ b/tests/test-help.t
@@ -1502,6 +1502,8 @@ Separate sections from subsections
   
       "usestore"
   
+      "sparse-revlog"
+  
       "profiling"
       -----------