Create a more compact diff format

[oli-obk]

An example showcasing all the possible render combinations

[bors]

☔ The latest upstream changes (presumably #2373) made this pull request unmergeable. Please resolve the merge conflicts.

[RalfJung]

Some "N lines skipped" have "..." after them and some not -- what's up with that?

Is it possible to always print a few lines around where things changed, for context (the way diff -u does)?

[oli-obk]

Is it possible to always print a few lines around where things changed, for context (the way diff -u does)?

done

@rustbot review

[RalfJung]

I think I'm going to have to just trust you on this one, since that row function would be a lot of effort to review properly. I don't know the API it interacts with and it has very few comments. print_skip has no comments at all.

Can you show how an example diff look like now?

[oli-obk]

I think I'm going to have to just trust you on this one

My plan was to just see how it goes in practice and adjust it if we see problems. Worst case is just some badly rendered diffs

[oli-obk]

two random missing lines in a stderr cause:

at the two line skip point:

when only one line would be skipped:

when just some chars change in a line:

when you both add and remove chars from a line:

when you do larger diffs:

the last one is not great... I could make it like "more than half of the chars must be the same"

[RalfJung]

Nice!

I think the one thing I am missing is whether - or + is the reference output vs actual output. Regular diff starts with a header like

--- build.rs    2022-07-25 12:43:20.977864910 -0400
+++ Cargo.toml  2022-07-25 12:43:20.977864910 -0400

that makes this quite clear; should we have something similar?

[RalfJung]

Also, does this always print the first and last line? Not that I object, just a bit surprising. In particular it seems to be the first two lines and the last one line, which is strangely asymmetric?

[RalfJung]

@rustbot author

[bors]

☔ The latest upstream changes (presumably #2449) made this pull request unmergeable. Please resolve the merge conflicts.

[oli-obk]

continued in oli-obk/ui_test#8