documentation: help: add "man.<tool>.path" config variable

This patch documents the "man.<tool>.path" configuration
variable.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -805,6 +805,10 @@ merge.<driver>.recursive::
 	performing an internal merge between common ancestors.
 	See linkgit:gitattributes[5] for details.
 
+man.<tool>.path::
+	Override the path for the given tool that may be used to
+	display help in the 'man' format. See linkgit:git-help[1].
+
 mergetool.<tool>.path::
 	Override the path for the given tool.  This is useful in case
 	your tool is not in the PATH.

Documentation/git-help.txt

@@ -104,6 +104,15 @@ DISPLAY is not set) and in that case emacs' woman mode will be tried.
 
 If everything fails the 'man' program will be tried anyway.
 
+man.<tool>.path
+~~~~~~~~~~~~~~~
+
+You can explicitly provide a full path to your preferred man viewer by
+setting the configuration variable 'man.<tool>.path'. For example, you
+can configure the absolute path to konqueror by setting
+'man.konqueror.path'. Otherwise, 'git help' assumes the tool is
+available in PATH.
+
 Note about git config --global
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~