runewidth.StringWidth is an expensive call, even if the input string is pure
ASCII. Improve this by providing a wrapper that short-circuits the call to len
if the input is ASCII.
Benchmark results show that for non-ASCII strings it makes no noticable
difference, but for ASCII strings it provides a more than 200x speedup.
BenchmarkStringWidthAsciiOriginal-10 718135 1637 ns/op
BenchmarkStringWidthAsciiOptimized-10 159197538 7.545 ns/op
BenchmarkStringWidthNonAsciiOriginal-10 486290 2391 ns/op
BenchmarkStringWidthNonAsciiOptimized-10 502286 2383 ns/op
As part of this, you must now press enter on a merge conflict file
to focus the merge view; you can no longer press space and if you do
it will raise an error.
We will pass these positions back to clients for rendering non-model items, and
it's important that clients can consistently rely on them no matter which
columns were removed.
We've been sometimes using lo and sometimes using my slices package, and we need to pick one
for consistency. Lo is more extensive and better maintained so we're going with that.
My slices package was a superset of go's own slices package so in some places I've just used
the official one (the methods were just wrappers anyway).
I've also moved the remaining methods into the utils package.
