irunner command line options defer to file extensions

[juliantaylor]

Running irunner --ipython script.py currently sees the .py extension, and chooses the Python runner. Command line options should probably override file extensions.

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Original bug report:

when running irunner from git head with --interact or -i:

$ irunner --interact /tmp/test.py
Usage:
irunner [options] file_to_run

...

irunner: error: no such option: --interact

also the --ipython option does not seem to work, it has regular python prompts and not the ipython prompts:
$ irunner /tmp/test.py

print "test"

[juliantaylor]

forget that I am just to stupid to read the help message:
irunner --ipython -- --interact script.py works

[takluyver]

It seems that the file extension takes priority over the options passed, so a .py file is run in PythonRunner. It makes sense that the command line flags should have priority over file extensions, and it should be easy to change.

For --interact, make sure you follow the instructions in the usage message - you need an extra -- in before options that will be parsed to the underlying process. If I do this, it seems to work.

[takluyver]

Reopened because I think the command line options should take priority over file extensions, but it's lower priority.

[takluyver]

Merged in at 10c2367.