How to recover lost Python source code if it's still resident in a running inter (2017)

In the "old days", an open file was in memory, and you needed to explicitly save it with Save, or save a new version with Save As.

But now everything's flown out the window. If I open a PDF in Preview on my Mac and delete a page from it, it saves the change instantly. If I made a mistake, I can't just close it and re-open the original version. I have to use "File > Revert to > Browse All Versions..."

But it acts differently if my file is on an external drive which doesn't support MacOS file revisions, so when I close the file it gives me this scary long dialog to explicitly make a choice whether to keep my changes or revert, this is my last chance.

Oh and there's no Save As anymore, there's a "File > Duplicate" instead which is never what I want, because the whole point is that sometimes I want to save my changes in a new file but keep the old one without the changes. So I have to do a whole song-and-dance to first duplicate and then save that and then go back to the original and then revert that.

Except it all depends on the application. Some applications still have the traditional Save / Save As, while some have moved onto Duplicate / Revert.

And as you mention, some apps will update the file you have open to reflect changes on disk, while others won't.

And of course cloud apps in the browser just autosave the whole time.

So you have to keep this insanely complex matrix in your head to figure out whether you need to constantly save your work with Cmd+S or not, or whether your work will accidentally overwrite your previous version which you might have been intending to save, or whether something like a sync will overwite the work you have open, and it all depends on just on which application you're using, but whether it's a cloud version or not, and whether you're working off of an external drive or not!

It's maddening. I hate it.

I learned a valuable lesson that day about testing recovery from backups before you need them. I also learned a lesson about only running commands in a root shell when you really need to be root.

Even if it's in the object store though, it may be hard to find; if it was never commited, it was only ever referenced by the index, and now it's completely unrereferenced. Maybe you could enumerate all unreachable blobs, diff them with the current version of the file, and manually review all the blobs where the diff size is below some threshold.