new flag: Enable renaming during file upload if duplicate exists

[Atreyagaurav]

Fixes #1452

I think this will work as a flag to rename files. It won't work when the file contains multiple extension like .tar.gz which is hard to do, as we could make it work with that, but any file with multiple . in the text for no meaning will mess it up. But I can make that change if you think that's acceptable.

Also, it will break compatibility, but we could combine the overwrite and rename flags into a single flag like --duplicate-files that takes enum (rename/overwrite).

[Atreyagaurav]

I also thought about just renaming when overwrite is false instead of error. Which is probably a reasonable thing to do as well. Let me know what you think.

[svenstaro]

Thanks for this! I'd really like to see some tests here, though. It just occurred to me that we have no tests for conflicting files without any flags set nor did we have one for --overwrite-files. Would be up for making a bunch of tests showing

1. Overwriting files is not possible without extra flags
2. --overwrite-files works as expected
3. --rename-duplicate works as expected
   ?

I also thought about just renaming when overwrite is false instead of error. Which is probably a reasonable thing to do as well. Let me know what you think.

I think we want an error here by default. It's safer.

Also, it will break compatibility, but we could combine the overwrite and rename flags into a single flag like --duplicate-files that takes enum (rename/overwrite).

I do like the enum idea. I'm fine breaking compatibility here. We have to make sure it's well pointed out in the CHANGELOG so people can quickly spot it.

[Atreyagaurav]

Thanks for the review, I'll push with the tests once I have a bit more free time.

[Atreyagaurav]

I have added the tests for the three conditions mentioned previously.

I copied the tests from the upload_file test, and modified them. The test are for failing to upload a duplicate file, checking overwrite with new contents, and checking rename flag that creates an additional file.

[svenstaro]

@Atreyagaurav Looking great! What do you think about the enum thing that we discussed above?

[Atreyagaurav]

I added it as enum, and made the default be error. So only breaking change is
-o needs a value as it is no longer bool. and --overwrite-files is not available. I named the new flag on-duplicate-files

I have the tests updated as well. And I also manually tested.