Accessing historical versions of the cloud copy of the dive log

Willem Ferguson willemferguson at
Mon Jun 17 13:20:33 PDT 2019

On 2019/06/17 20:38, Linus Torvalds wrote:
> On Sun, Jun 16, 2019 at 12:24 PM Willem Ferguson
> <willemferguson at> wrote:
>> For data security when something wrong has happened to a dive log, it
>> would be invaluable if one could request "Open die dive log as it was on
>> October 1st 2018". Is something like this in principle possible with
>> git?
> Git can maintain a per-branch log of when things changed, but libgit2
> (which we use) does not.
> Also, even if it were to be there, it's per-repository and doesn't get
> distributed out to the cloud (because by definition the dates when
> something happened are local - what you saw in one repo back in
> October might have showed up in another repository much later).
> So the date-based one is not going to be much of an option, although I
> guess we could add some way for people to at least see *when* some git
> commit was made.
>                  Linus

Thank you very much. You answered my question comprehensively. I have 
many things to think about.

One of the (quite a few) things that differentiates Subsurface from 
other equivalent software is the usage of a git repository as a dive 
log. It is not just another data format, comparable to XML or CSV. git 
is a whole infrastructure that strengthens dive log security immensely. 
And once  a diver has passed the 100 dive mark I would expect that data 
security is becoming an issue and the ability to recover from a stupid 
mistake or oversight is possible with git. I guess the rhetorical  
question is how could one make git work for a user who is not very 
computer savvy? And the answer to that question looks like "Yes, but it 
would require an enormous coding effort". I am pretty impressed with the 
ability to use Subsurface to open the dive log at a specific commit. I 
am going to try that one.

Thanks for your time.

Kind regards,


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