[kdenlive] Apologies and explanations

[Jean-Baptiste Mardelle]

Hi all,

As you might know, a recent bug in Kdenlive's git master caused major data 
loss to some users. I am deeply sorry about it and would like to provide 
some details about what happened, why and what we did and plan about it.

1- what happened:

In Kdenlive, we sometimes manage a lot of temporary data. As I was working 
on a new feature (timeline preview), it generated lots of temporary 
rendered videos. So at some point, this data needs to be deleted. To do 
this, I used a standard Qt class, QDir. However, if for some reason QDir is 
not correctly initialized or an operation fails, it defaults to your home 
directory. You can guess the end. As with many bugs, the error did not 
trigger everytime, so when I tried it before committing, I did not realize 
the possible problem.

2 - how could such stupid code be committed:

One of the reason it was committed is that I have been working too much in 
the last weeks. Working on Kdenlive is great, but at some point I went too 
far. Combined with my day job, I did not sleep enough and committed this 
stupid mistake. 

3 - what about the future, is it safe to use Kdenlive ?

As soon as I realized the extend of the problem, I commented out the 
problematic code and deleted the PPA packages. Git master is safe now, as 
is current kdenlive-master PPA built from the 26th of May :
kdenlive - 4:16.07.70+git201605260633~ubuntu16.04.1

Causing data loss on our users deeply affected me, and I think it should 
also be a big reminder for everyone that using a daily built development 
version from git is not safe, and that you must backup your data!

I will put a big warning now on the development version, and will discuss 
with Vincent about possible changes in our PPA/development policy to help 
prevent such problems.

I will also of course revise our temporary data handling to make sure such 
a mistake does not happen twice.

So again, I send my sincere apologies and hope we can continue to move 
forward in the next months.