tag: change default of `pager.tag` to "on"

The previous patch taught `git tag` to only respect `pager.tag` in
list-mode. That patch left the default value of `pager.tag` at "off".

After that patch, it makes sense to let the default value be "on"
instead, since it will help with listing many tags, but will not hurt
users of `git tag -a` as it would have before. Make that change. Update
documentation and tests.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/tag.c b/builtin/tag.c
index 5ad1af2..ea83df5 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -462,7 +462,7 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 	}
 
 	if (cmdmode == 'l')
-		setup_auto_pager("tag", 0);
+		setup_auto_pager("tag", 1);
 
 	if ((create_tag_object || force) && (cmdmode != 0))
 		usage_with_options(git_tag_usage, options);