Documentation/git-push.txt: correct configuration typo

In the EXAMPLES section, git-push(1) says that 'git push origin' pushes the current branch to the value of the 'remote.origin.merge' configuration. This wording (which dates back to b2ed944af7 (push: switch default from "matching" to "simple", 2013-01-04)) is incorrect. There is no such configuration as 'remote.<name>.merge'. This likely was originally intended to read "branch.<name>.merge" instead. Indeed, when 'push.default' is 'simple' (which is the default value, and is applicable in this scenario per "without additional configuration"), setup_push_upstream() dies if the branch's local name does not match 'branch.<name>.merge'. Correct this long-standing typo to resolve some recent confusion on the intended behavior of this example. Reported-by: Adam Sharafeddine <adam.shrfdn@gmail.com> Reported-by: Fabien Terrani <terranifabien@gmail.com> Signed-off-by: Taylor Blau <me@ttaylorr.com> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>