Comment by josephg | Hacker News Reader

Comment by josephg | Hacker News Reader

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I've played with this problem on and off over the last few years. ShareDB[1] is powered by JSON OT[2], in which each change describes the meaning behind what you're trying to do. (For example, 'increment counter' is different from 'change counter from 2 to 3'. They look the same, but behave differently in the case of conflicts). Just knowing what changed often isn't enough to do proper resolution.

I've spent years on and off playing with a better, faster, stronger version of the JSON OT code[1] which also supports arbitrary object reparenting. You run into problems where you really want conflicts as well. For example, given {x:{}, y:{}} user A moves x into y, and user B moves y into x. There's no good solution to resolving this without more information or conflict markers & humans.

Doing this in a P2P setting is hard & interesting. Very cool stuff though!

[1] https://github.com/share/sharedb [2] https://github.com/ottypes/json0 [3] https://github.com/josephg/json1

> Just knowing what changed often isn't enough to do proper resolution.

This is why my git commit logs are sometimes:

     perl -p -i -e 's/FOO/BAR/g' $(find src -name "*.[ch]" -print)

Having a "high level" description of what changed makes manual merges easier.

I wish git had conflict resolution like this. Treating data as an arbitrary sequence of bits is general and correct. Treating data as having a particular format can be useful, too.

It does? git merge --strategy xyz means git will invoke git-merge-xyz to do the actual conflict resolution. It comes with a variety of built-in ones (see https://git-scm.com/docs/merge-strategies) but you can write more if you have some special-purpose approach you want to use.

Git also has smudge/clean filters if you want to transform your file to a format where line-by-line textual merge is more meaningful

And you can use .gitattributes to make certain extensions/folders/file/whatever default to a certain treatment.

A good example is https://bitbucket.org/sippey/zippey which unpacks zip archives (and hence file formats based on them, like .jar, .docx, etc) to allow the contents within to be tracked in the git repo better. Other custom formats could do something similar...

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