Fixes #585.

@matteodepalo did a great job documenting the issue, so I'm not going to repeat it here.

Context

Ink has two ways of rendering output, depending how tall it is:

1. If output is shorter than terminal height, Ink erases the lines from last output and writes lines from the new output. Ink tracks how many lines did the last output have for this to work. This is handled in https://github.com/vadimdemedes/ink/blob/master/src/log-update.ts, which is a fork of log-update package.

2. If output is equal or taller than terminal height, Ink erases the entire terminal history (or scrollback as it's commonly referred to) and writes new output. Note that Ink doesn't need to track how many lines to erase here, because it just erases the entire contents of the current terminal.
   

   ink/src/ink.tsx

   Lines 176 to 182 in 8a04760

   	if (outputHeight >= this.options.stdout.rows) {
   	this.options.stdout.write(
   	ansiEscapes.clearTerminal + this.fullStaticOutput + output
   	);
   	this.lastOutput = output;
   	return;
   	}

Root cause

The key insight here is this:

Note that Ink doesn't need to track how many lines to erase here, because it just erases the entire contents of the current terminal.

In #585, the very first render starts with the second rendering method and erases the terminal completely. On next render, the first method kicks in, but there's no information how many lines to erase, since second method doesn't store that information.

That's why the output from the first render doesn't get erased, since for logUpdate this variable is zero.

Solution

This PR fixes this bug by separating the write operation that erases the terminal and writes the output. This way, even if the entire terminal is erased, logUpdate is still used to render the output and keep track of how many lines were written.

I've also added force option to logUpdate render function to force it to always render the string we give to it without bailing out if it equals to the last output. This can happen when Static output changes, but normal output isn't.

I've also added erase option to logUpdate render function, so that we can tell it to not do erasing of its own, if we erased the entire terminal already.