Improve condition to determine if the output file is executable or not

slapos/recipe/template/__init__.py

@@ -108,8 +108,18 @@ class Recipe(object):
         output = self.output
         rendered = self._render()
         mode = self.mode
-        mask = (0o777 if rendered.startswith(b'#!') else 0o666
-               ) if mode is None else 0
+        if mode is None:
+            mask = 0o666
+            if rendered.startswith(b'#!'):
+                try:
+                    x = rendered.index(b'\n', 2)
+                except ValueError:
+                    x = len(rendered)
+                x = rendered[2:x].split(None, 1)
+                if x and os.access(x[0], os.X_OK):
+                    mask = 0o777
+        else:
+            mask = 0
         # Try to reuse existing file. This is particularly
         # important to avoid excessive IO because we may render on update.
         try: