Blender Git Loki

Accept non-existing files from the CLI

When a user tries to load a non-existing blend file from the CLI, the path
is set and Blender acts as if it is loaded. This allows the user to create
a new file by typing 'blender filename.blend' and then saving. This
behaviour is common in other tooling, such as vim and Mypaint.

Blender's current behaviour (print an error message and open the default
scene) doesn't make much sense. It ignores the filename passed on the CLI,
whereas with this patch that filename is actually remembered, and used when
saving.

Reviewers: campbellbarton, sergey, mont29