contrib/subtree: there's no push --squash

The documentation says that --squash is for 'add', 'merge',
'pull' and 'push', while --squash actually doesn't change
the behavior of 'push'. Correct the documentation.

Signed-off-by: Danny Lin <danny0838@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/subtree/git-subtree.sh

@@ -26,7 +26,7 @@ b,branch=     create a new branch from the split subtree
 ignore-joins  ignore prior --rejoin commits
 onto=         try connecting new tree to an existing one
 rejoin        merge the new branch back into HEAD
- options for 'add', 'merge', 'pull' and 'push'
+ options for 'add', 'merge', and 'pull'
 squash        merge subtree changes as a single commit
 "
 eval "$(echo "$OPTS_SPEC" | git rev-parse --parseopt -- "$@" || echo exit $?)"

contrib/subtree/git-subtree.txt

@@ -146,7 +146,7 @@ OPTIONS
 OPTIONS FOR add, merge, push, pull
 ----------------------------------
 --squash::
-	This option is only valid for add, merge, push and pull
+	This option is only valid for add, merge, and pull
 	commands.
 +
 Instead of merging the entire history from the subtree project, produce