Amend git-push refspec documentation

These paragraphs are a little confusing.  Also, make it clearer when
you have to specify the full name for <dst>

Signed-off-by: Sam Vilain <sam.vilain@catalyst.net.nz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -35,14 +35,15 @@ OPTIONS
 	by the source ref, followed by a colon `:`, followed by
 	the destination ref.
 +
-The <src> side can be an
-arbitrary "SHA1 expression" that can be used as an
-argument to `git-cat-file -t`.  E.g. `master~4` (push
-four parents before the current master head).
+The <src> side represents the source branch (or arbitrary
+"SHA1 expression", such as `master~4` (four parents before the
+tip of `master` branch); see linkgit:git-rev-parse[1]) that you
+want to push.  The <dst> side represents the destination location.
 +
 The local ref that matches <src> is used
-to fast forward the remote ref that matches <dst>.  If
-the optional plus `+` is used, the remote ref is updated
+to fast forward the remote ref that matches <dst> (or, if no <dst> was
+specified, the same ref that <src> referred to locally).  If
+the optional leading plus `+` is used, the remote ref is updated
 even if it does not result in a fast forward update.
 +
 Note: If no explicit refspec is found, (that is neither
@@ -165,7 +166,8 @@ git push origin master::
 	Find a ref that matches `master` in the source repository
 	(most likely, it would find `refs/heads/master`), and update
 	the same ref (e.g. `refs/heads/master`) in `origin` repository
-	with it.
+	with it.  If `master` did not exist remotely, it would be
+	created.
 
 git push origin :experimental::
 	Find a ref that matches `experimental` in the `origin` repository
@@ -179,9 +181,10 @@ git push origin master:satellite/master::
 
 git push origin master:refs/heads/experimental::
 	Create the branch `experimental` in the `origin` repository
-	by copying the current `master` branch.  This form is usually
-	needed to create a new branch in the remote repository as
-	there is no `experimental` branch to match.
+	by copying the current `master` branch.  This form is only
+	needed to create a new branch or tag in the remote repository when
+	the local name and the remote name are different; otherwise,
+	the ref name on its own will work.
 
 Author
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