Fix file serving for files with absolute paths

[lukeyeager]

Bug reported at https://groups.google.com/d/msg/digits-users/MW_kHbOEqNo/y7wXpvlSFAAJ

To reproduce:

• Create a dataset from textfiles on the server (i.e. enter the path on the server manually)
• Click on the textfile from the DatasetJob page
• Get a 404 error because the path is wrong

[gheinrich]

I don't see this issue on master, is this because I'm using a devserver and the source install?
For example when I click on a path like /home/greg/ws/digits/digits/jobs/20160117-131355-ba71/train.txt I seem to be correctly directed to http://localhost:5000/files/20160117-131355-ba71/train.txt and I can see the contents of the file.

[lukeyeager]

That still works because the file you're using is in the jobs directory. Try one on your desktop, for example.

[gheinrich]

Indeed! Moving the .txt files to /tmp/text/*.txt, now with your fix at 08f73e5 I don't get links to text files any more on the dataset job page. Is it expected?

[lukeyeager]

I don't get links to text files any more on the dataset job page. Is it expected?

That is what I meant to do, yes. But I admit it's a little confusing/disappointing.

The serve_file route only serves up files from within the jobs directory. That's for security and because it integrates with nginx more easily. See this comment:

# https://github.com/NVIDIA/DIGITS/blob/v3.2.0/digits/views.py#L319-L328
def serve_file(path):
    """
    Return a file in the jobs directory
    If you install the nginx.site file, nginx will serve files instead
    and this path will never be used
    """
    jobs_dir = config_value('jobs_dir')
    return flask.send_from_directory(jobs_dir, path)

[gheinrich]

unrelated with this change but that code duplication makes it look like Task and Job classes could share a common ancestor

[gheinrich]

Beside #593 the change looks good to me and is working for me.