Add a "duplicate notebook" option that keeps the old and new workbooks open

[JasonWeill]

The option to duplicate the current notebook doesn't exist any more. I'm guessing "Save as" is the replacement. However, after using this, whilst the newly named notebook pops up in a new tab correctly, the old tab no longer works -- the notebook disappears and the error "kernel unknown" appears. The desired behavior is to have both the new and old notebooks running in separate kernels in separate windows/tabs.

Originally reported by @jph00 in #7041 (comment).

In JupyterLab there is "Duplicate Notebook" option which was recently exposed in command palette and in the tab context menu jupyterlab/jupyterlab#12870. It appears to be an unintentional omission that it was left out in Notebook, it would be a good first issue to restore it by adding docmanager:duplicate to menus and command palette where needed (which might be as simple as just changing a few JSON files, see jupyterlab/jupyterlab#12870)

There is also a button in the tree view:

Reply posted by @krassowski in #7041 (comment).

[JasonWeill]

There is already a "duplicate" option in the context menu that appears when I right-click on a file in the tree view.

[ai-robert]

@JasonWeill @jtpio the "duplicate" option being requested there isn't the one pointed out in that screenshot but rather it's missing from the notebook interface. in Jupyter v6 A super common pattern in the notebook interface is to be working on a notebook, and if you want to branch off into different ideas, or keep a cleaner master notebook and then create a duplicate to scratch out some new ideas, is to (within the notebook interface) quickly hit File > "Make a Copy" (sometimes a few times at once) and start picking up right where you left off. Forcing the user to switch to the jupyter hub interface, duplicate, then open the notebook, then switch back... not good... By the way the behavior I'm mentioning for v7 are for the anaconda bundled v7.0.8 and the pypi version 7.2.x. Forgive me if you pushed an update to pypi in the past two weeks I've been under a crunch between my first ticket and this comment

[jtpio]

in Jupyter v6 A super common pattern in the notebook interface is to be working on a notebook, and if you want to branch off into different ideas, or keep a cleaner master notebook and then create a duplicate to scratch out some new ideas, is to (within the notebook interface) quickly hit File > "Make a Copy" (sometimes a few times at once) and start picking up right where you left off.

Isn't it what was implemented in #7374 (see screencast on that PR), which should now be available in the latest 7.x releases?

[krassowski]

Isn't it what was implemented in #7374 (see screencast on that PR),

Yes

which should now be available in the latest 7.x releases?

I think it is not, as that PR was tagged for 7.3 which has not been released yet, right?

[jtpio]

I think it is not, as that PR was tagged for 7.3 which has not been released yet, right?

Ah right, I thought it was released in 7.2.0 already.

@ai-robert so this should be released in the upcoming 7.3.0 release. Still need to unblock #7423 to make a new pre-release.