Documentation: improve phrasing in git-push.txt

The current version contains the sentence:

Further suppose that the other person already pushed changes leading to
A back to the original repository you two obtained the original commit
X.

which doesn't parse for me; I've changed it to

Further suppose that the other person already pushed changes leading to
A back to the original repository from which you two obtained the
original commit X.

Signed-off-by: Mark Szepieniec <mszepien@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -286,7 +286,8 @@ leading to commit A.  The history looks like this:
 ----------------
 
 Further suppose that the other person already pushed changes leading to A
-back to the original repository you two obtained the original commit X.
+back to the original repository from which you two obtained the original
+commit X.
 
 The push done by the other person updated the branch that used to point at
 commit X to point at commit A.  It is a fast-forward.