create and overwrite automatic snapshots, but save the last one from each session permanently

[GoogleCodeExporter]

Currently, a snapshot is only saved when the user hits the "Save" button. Apart 
from that, cell contents are saved to the current version whenever a cell is 
evaluated. Sometimes, when a worksheet is closed and re-opened, Firefox for 
some reason uses an old version of the worksheet, and when the user evaluates 
the cells again, the ones saved previously are overwritten with the current 
version in Firefox. This cannot be undone unless the user actively generated a 
snapshot in the mean time. Well, it could be undone by finding the changes in 
the history and copying and pasting from there, but this is tedious. To improve 
recoverability of previous work, I would like to suggest the generation of 
automatic snapshots every few minutes that are over-written, keeping only the 
most up-to-date one. If the worksheet is closed or the computer crashes, there 
would always be a snapshot stored that is only a few minutes old. Upon 
re-opening of the worksheet, the snapshot should be treated like a permanent 
one and not be overwritten by the automatic snapshots. This would ensure that 
the user always has at least one snapshot of his worksheets from each session. 
This would not lead to an excessive number of snapshots, but would tremendously 
increase the user's piece of mind.

Original issue reported on code.google.com by schym...@gmail.com on 7 Oct 2011 at 12:04

[GoogleCodeExporter]

Isn't this what we *disabled* a few years back because it was a process hog?  I 
do agree we should do more autosaves, but need a balance.

Original comment by kcris...@gmail.com on 7 Oct 2011 at 4:40

[GoogleCodeExporter]

We threw the baby out with the bath water. The problem was that there were
too many snap shots saved, but disabling them altogether was very
counterproductive in my view.

Am 07.10.2011 18:41 schrieb <sagenb@googlecode.com>:

Original comment by schym...@gmail.com on 7 Oct 2011 at 7:05

[GoogleCodeExporter]

I changed things slightly in the new flask notebook.  Before, it aborted saving 
a snapshot if the on-disk html was the same as what was in memory.  I took out 
this early-abort, so that clicking on Save always saves a snapshot.

Original comment by jason-go...@creativetrax.com on 18 Oct 2011 at 6:07

[GoogleCodeExporter]

But this didn't even seem to work before anyway.  See issue 59.

Original comment by kcris...@gmail.com on 18 Oct 2011 at 6:56

[GoogleCodeExporter]

Yep, I believe that issue 59 is still a problem in test.sagenb.org

Original comment by jason-go...@creativetrax.com on 18 Oct 2011 at 6:59

[GoogleCodeExporter]

I can confirm that issue 59 still is a problem in test.sagenb.org, meaning that 
there is no point addressing Issue 58 at present. Unless the automatic 
snapshots are processed differently to the ones generated by pressing "Save", 
which they probably should be. Ideally, there should be no way to overwrite 
snapshots generated by pressing "Save", while the automatically generated 
snapshots should be overwritten automatically according to the above suggestion.

Original comment by schym...@gmail.com on 19 Oct 2011 at 10:27

[GoogleCodeExporter]

Another interesting behaviour to notice:
Create a snapshot, then keep adding lines to the worksheet, then logout from 
test.sagenb.org without saving or discarding, then login again, re-open the 
worksheet and hooray, the unsaved changes are still there. However, the 
previous snapshots have been updated, too, so they reflect the unsaved changes. 
If I create a new document and don't save any snapshots, the latest version is 
also recovered after logut and login, but the revisions list does not contain 
any revisions. 

Not sure what is happening there.

Original comment by schym...@gmail.com on 24 Oct 2011 at 2:39

[GoogleCodeExporter]

Similar question in true upstream.

Original comment by kcris...@gmail.com on 3 Dec 2014 at 8:31