git-push.txt: document the behavior of --repo

As per the code, the --repo <repo> option is equivalent to the
<repo> argument to 'git push', but somehow it was documented as
something that is more than that.  [It exists for historical
reasons, back from the time when options had to come before
arguments.]

Say so. [But not that.]

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -207,22 +207,8 @@ origin +master` to force a push to the `master` branch). See the
 `<refspec>...` section above for details.
 
 --repo=<repository>::
-	This option is only relevant if no <repository> argument is
-	passed in the invocation. In this case, 'git push' derives the
-	remote name from the current branch: If it tracks a remote
-	branch, then that remote repository is pushed to. Otherwise,
-	the name "origin" is used. For this latter case, this option
-	can be used to override the name "origin". In other words,
-	the difference between these two commands
-+
---------------------------
-git push public         #1
-git push --repo=public  #2
---------------------------
-+
-is that #1 always pushes to "public" whereas #2 pushes to "public"
-only if the current branch does not track a remote branch. This is
-useful if you write an alias or script around 'git push'.
+	This option is equivalent to the <repository> argument. If both
+	are specified, the command-line argument takes precedence.
 
 -u::
 --set-upstream::