CLI overwrites without warning

[dsblank]

If I call the CLI to output a particular format, it will overwrite existing file named the same.

Suggestions:

1. give a warning that it overwrote file
2. require a --force flag to overwrite
3. put a unique number on new file

In general, it would be nice for the CLI to give some feedback about what it read in, and what it created.

[mwouts]

Hello @dsblank , thanks for reporting. When I compare with jupyter nbconvert is see that nbconvert also overrides the output file. Sure, this can be a surprise to the user, but this is a CLI, isn't it?

I agree that the CLI could tell a bit more about what it is doing (format detected in the file, output file, format, whever it tries to preserve outputs, etc). Would you like to submit a PR (on v0.8.4 if possible)? Please keep in mind that people may be using the command line to convert document in batches, and may also pipe notebooks into it (stdin and stdout are supported).

[dsblank]

Sure, I'll try to look at this in the next few days (unless someone beats me to it). Thanks!

[mwouts]

Available in v0.8.4