Put in the two other configuration elements found in the source

I am not entirely clear what these parameters do but felt it
 useful to call them out in the documentation.

Signed-off-by: Anand Kumria <wildfire@progsoc.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/fast-import/git-p4.txt

@@ -163,6 +163,10 @@ Specify the client name to use
 
   git config [--global] git-p4.client public-view
 
+git-p4.allowSubmit
+
+  git config [--global] git-p4.allowSubmit false
+
 git-p4.syncFromOrigin
 
 A useful setup may be that you have a periodically updated git repository
@@ -176,6 +180,10 @@ by default if there is an origin branch. You can disable this using:
 
   git config [--global] git-p4.syncFromOrigin false
 
+git-p4.useclientspec
+
+  git config [--global] git-p4.useclientspec false
+
 Implementation Details...
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