Documentation: instaweb: add 'git-web--browse' information.

Now that 'git-instaweb' uses 'git-web--browse', update the
documentation accordingly.

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

Documentation/git-instaweb.txt

@@ -38,10 +38,23 @@ OPTIONS
 	The port number to bind the httpd to.  (Default: 1234)
 
 -b|--browser::
-
-	The web browser command-line to execute to view the gitweb page.
-	If blank, the URL of the gitweb instance will be printed to
-	stdout.  (Default: 'firefox')
+	The web browser that should be used to view the gitweb
+	page. This will be passed to the 'git-web--browse' helper
+	script along with the URL of the gitweb instance. If the
+	script fails, the URL will be printed to stdout.
++
+Note that the 'git-web--browse' script tries, as much as possible, to
+display the HTML page in a new tab on an already opened browser.
++
+The following browsers are currently supported by 'git-web--browse':
++
+* firefox (this is the default under X Window when not using KDE)
+* iceweasel
+* konqueror (this is the default under KDE)
+* w3m (this is the default outside X Window)
+* links
+* lynx
+* dillo
 
 --start::
 	Start the httpd instance and exit.  This does not generate
@@ -74,6 +87,12 @@ You may specify configuration in your .git/config
 If the configuration variable 'instaweb.browser' is not set,
 'web.browser' will be used instead if it is defined.
 
+You can explicitly provide a full path to your preferred browser by
+setting the configuration variable 'browser.<tool>.path'. For example,
+you can configure the absolute path to firefox by setting
+'browser.firefox.path'. Otherwise, 'git-web--browse' assumes the tool
+is available in PATH.
+
 Author
 ------
 Written by Eric Wong <normalperson@yhbt.net>