[ILUG] File syncing

[Gareth Eason]

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Bernhard Rohrer wrote:
|>> There are lots of tools that can sync two locations, but i don't know
|>> any that will deal with save conflicts if both files (remote and
|>> local) was edited, and i don't want to loose either files changes.
|
| not doable IMO. Notes doesn't do it and it is the best piece of software
| for that kind of thing on the planet.

	Agreed - unless you have some further information on the types of
changes or how the file works. For example - source code can often be
intelligently 'merged' if the changes are in radically different offsets
in the file and the system knows that C Source code (for example) is
linear and not checksummed based on total content - so it's likely to work.

	Things like etc-update on gentoo understand the concept of comments and
will 'trivially auto-merge' files that only differ due to whitespace or
comments. Again, it can only do this because it knows something about
the format and meaning of contents of the file.

	For generic recovery from split-brain state (which is possibly(?) the
most common reason for the 'same' file being changed in two places at
once and then having to be merged) there is no generic method of
ensuring that both sets of changes are included and that the file is
correct after a merge. Human intervention is required.

	I'd suggest that you should aim for something that will either lock
files so they can only be edited in one place at a time - or else take
your chances that files will be sync'ed quickly enough after changes are
made in one place, that it's statistically likely that they've
propogated by the time someone tries to edit it from the other place. In
practice, this works surprisingly well, since people naturally tend to
work on one file at a time. However, you may have to merge files
periodically, so make sure you have a manual process in place to do this.

	Hope this explains the problem a bit better and maybe even alludes to
some kind of solution that's appropriate for your needs.

	Best regards,
	-->Gar

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