Only use non-empty --shell-arg values

This allows --shell=python --shell-arg='' to override /bin/sh.

1 files changed, 1 insertions, 1 deletions

diff --git a/yarn b/yarn
index a18aa8e..7d3b295 100755
--- a/yarn
+++ b/yarn
@@ -455,7 +455,7 @@ class YarnRunner(cliapp.Application):
             f.write(step.implementation.shell)
             f.flush()
         shell = self.settings['shell']
-        shell_args = self.settings['shell-arg']
+        shell_args = [x for x in self.settings['shell-arg'] if x]
         logging.warning('shell: %r', shell)
         logging.warning('shell_args: %r', shell_args)
         logging.warning('shell_script: %r', shell_script)