git-clone.txt: remove the restriction on pushing from a shallow clone

The document says one cannot push from a shallow clone. But that is
not true (maybe it was at some point in the past). The client does not
stop such a push nor does it give any indication to the receiver that
this is a shallow push. If the receiver accepts it, it's in.

Since 52fed6e (receive-pack: check connectivity before concluding "git
push" - 2011-09-02), receive-pack is prepared to deal with broken
push, a shallow push can't cause any corruption. Update the document
to reflect that.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-clone.txt

@@ -182,11 +182,13 @@ objects from the source repository into a pack in the cloned repository.
 --depth <depth>::
 	Create a 'shallow' clone with a history truncated to the
 	specified number of revisions.  A shallow repository has a
-	number of limitations (you cannot clone or fetch from
-	it, nor push from nor into it), but is adequate if you
-	are only interested in the recent history of a large project
-	with a long history, and would want to send in fixes
-	as patches.
+	number of limitations (you cannot clone or fetch from it, nor
+	push into it), but is adequate if you are only interested in
+	the recent history of a large project with a long history.
++
+Pushing from a shallow clone should be avoided if the git version on
+the receiver end is older than v1.7.10, or any other git
+implementation that does not perform connectivity check.
 
 --[no-]single-branch::
 	Clone only the history leading to the tip of a single branch,