Add Text::update

[alexjg]

Problem: sometimes when modifying text you are not able to capture the edits to the text field as they happen. For example, if the text is in a file and you just get notified when the file has changed then you have no way of knowing which text was inserted and deleted. The Text API requires that you express all changes as splice calls, so the user is forced to figure out how to turn the new value into a set of splice calls, which can be tricky.

Solution: add Text::update, which performs an LCS diff to figure out a minimal set of splice calls to perform internally.

[tdomhan]

This looks useful.
How does this relate to automerge/automerge@26472cd ?
With the updateText in automerge would you call that directly?

[alexjg]

Man I forgot I didn't merge this PR, I'm going to do that now.

Re. automerge::update_text, we couldn't use that here because the purpose of Text is to accumulate changes when you don't have mutable access to an automerge::Automerge for whatever reason. The result is ultimately the same (a sequence of splice calls based on the diff) and even uses the same algorithm because in the implementation of automerge::update_text I just cribbed the myers diff implementation from similar (with appropriate attribution of course) which is what we use here.

[tdomhan]

Makes sense, thanks!

[alexjg]

Published in 0.8.3