Warn before overwriting newer version of file

[Manjit Karve]

I love Inkscape and I use it as my primary design tool. Thank you, all, who contribute to it.

I recently lost quite a bit of work by overwriting my more recently saved file with an older one that had been open for days, in another Inkscape session in another workspace. My fault. But I know this could've been avoided had there been a few warnings:
1. Warn when opening the same file in different sessions.
2. Warn and allow reloading of a file that has been modified by another process.
3. Warn when overwriting a file with a remembered last-modified timestamp that's older than the target file's current last-modified timestamp.

Repro Steps:
1. Save an SVG file in Inkscape (instance-1): a.svg
2. Open a.svg in another Inkscape instance (instance-2)
3. Switch to instance-1.
4. Modify a.svg in instance-1 and save it.
5. Switch to instance-2.
6. Modify a.svg in instance-2 and save it.
7. Changes from step 4 are lost.

Environment:
Inkscape version 0.92.3
OS & version: Ubuntu Desktop 16.04.4

Expected behavior:
a) At step 2, Inkscape should warn that the file is open in another instance and give the user the option to switch to that instance or open the file again anyway.
b) At step 5, Inkscape should warn that the file has been modified by another process and give the user the option to reload the file from disk (and that local changes might be lost) or ignore external modification at this time.
c) At step 6, Inkscape should warn that the file has been modified elsewhere and saved since it had been opened in instance-2 and that the user needs to choose between saving the file anyway, saving under another name or cancel saving (and by implication, an application exit).

Observed behavior:
a) At step 2, Inkscape allows file to be opened without any indication that it has been opened elsewhere.
b) At step 5, Inkscape isn't aware that the file has been modified elsewhere.
c) At step 6, Inkscape allows overwriting the file without any warning.

Other observations:
The expected behavior can be observed in gedit which handles these situations as listed. Even implementing the warning from expected-behavior-c should be enough to avoid most cases of loss of work.

[Victor Westmann (victor.westmann)]

2018-07-12 VictorWestmann - +1 for this. Really useful enhancement.

[grey tomorrow (gtomorrow)]

Hi - thanks for reporting this bug, I've manually migrated it to Inkscape's new bug tracker on GitLab, and closed it here.

Please feel free to file new bugs about the issues you're seeing at
https://inkscape.org/report .

Moved to: https://gitlab.com/inkscape/inbox/issues/2493
Closed by: https://gitlab.com/greytomorrow