[Unison-hackers] Ignore files above a certain size

[Alan Schmitt]

Benjamin C. Pierce writes:

> An even easier way is to deal with such files at reconciliation time.
> We've already got mechanisms and preferences for overriding Unison's
> default reconciliation decisions based on many sorts of conditions
> (which file is newer, etc.). The downside is that large files will
> not, then, be completely ignored -- they will show up in the user
> interface as conflicts.

I think that's a good thing that they show up in the interface, so that
the user may decide to propagate them anyway.

Looking at the code, it seems the simplest is to extend shouldCancel for
this. This is much nicer than the "Error" approach: if A is deleted and
B is unchanged but above the limit, in the "Error" approach nothing
happens, in the "shouldCancel" approach B is deleted.

I was also looking at how to log which files have not been transferred
because of their size, and one way to do it is to add an argument to
Conflict (similar to the one for Problem) that gives the cause of the
conflict. This way it would be in the log and could be use in the UIs.

> Arguably, the right thing to do is to truly ignore such files. This
> will be a bit harder to implement, since it will have to start with
> generalizing the current ignore mechanism to take into account current
> information from the filesystem beyond just path names. And it will
> require a bit of care in reconciliation (because a file may then be
> ignored on one side and not the other and we'll want to make sure we
> correctly detect this situation and don't do something silly like
> delete one of the copies) and in the UI (because we'll have to report
> such situations to the user in some sensible way), as well as some
> thinking at the level of the formal spec to make sure that we can make
> sense out of such possibilities. But if we can figure out how to do it
> nicely, it would open the door to all sorts of further extensions that
> people have been asking for for years, like per-directory
> .unisonignore files.

I agree it would be a more general approach, but it requires many more
changes as you said.

Alan