Re: Using hash instead of timestamps to check for changes.

[Eric Melski]

On 04/11/2015 08:38 AM, Enrico Weigelt, metux IT consult wrote:
> On 07.04.2015 00:17, Eric Melski wrote:
>
> Hi,
>
> > This problem is relatively common when using an SCM system that
> > preserves *checkin* time on files rather than *checkout* time.
>
> I'd consider that a misbehavious of the SCM (IMHO, that's the reason
> why Git does not track the mtime). From the filesystem perspective,
> the mtime represents the time when the actual file was changed in the
> filesystem. So, resetting the mtime from some SCM repo actually is
> tricking the filesystem - pretty obvious that the mtime then isn't
> reliable anymore.

It doesn't necessarily require "resetting" or "manipulating" the mtime 
at all.  ClearCase has its own filesystem, MVFS, which simply behaves 
the way I described.  In any case, it's not an utterly irrational 
position to consider the last modification time of a file tracked by the 
version control system to be the time that a new revision of the file 
was created.  That *is* the last modification time, after all.

However, this is not the place for this type of philosophical debate. 
The question at hand is whether or not make would benefit from a 
non-timestamp-based notion of "up-to-dateness", and the answer seems to 
be clearly yes, for this and other reasons mentioned elsewhere in this 
thread.

Regards,

Eric Melski
Chief Architect
Electric Cloud, Inc.
http://blog.melski.net/