scripts/feeds: silence git warning by selecting pull style

Silence the warning in git 2.27 about undefined fast-forward style
in git pull. Define "ff-only" as the style.

Signed-off-by: Hannu Nyman <[email protected]>

scripts/feeds

@@ -158,8 +158,8 @@ my %update_method = (
 		'init'          => "git clone --depth 1 '%s' '%s'",
 		'init_branch'   => "git clone --depth 1 --branch '%s' '%s' '%s'",
 		'init_commit'   => "git clone '%s' '%s' && cd '%s' && git checkout -b '%s' '%s' && cd -",
-		'update'	=> "git pull --ff",
-		'update_force'	=> "git pull --ff || (git reset --hard HEAD; git pull --ff; exit 1)",
+		'update'	=> "git pull --ff-only",
+		'update_force'	=> "git pull --ff-only || (git reset --hard HEAD; git pull --ff-only; exit 1)",
 		'post_update'	=> "git submodule update --init --recursive",
 		'controldir'	=> ".git",
 		'revision'	=> "git rev-parse --short HEAD | tr -d '\n'"},