Tracking Incremental Changes (Avoid re-running builds)

[garrett-hopper]

Is there a recommended way of tracking when files in a folder change and only re-running a build when it would actually create a new artifact?
I know just is 'just' a task runner, but using it is far more desirable then Makefiles. Having a good way of doing this kind of incremental builds (running just twice in a row would cause the second run to do nothing) would be great.
I suppose the user may need to have a system to generate a hash of the folder/files that they depend on and implement their own check in their just targets. I don't know of any tools that could do this well though.

[casey]

Just doesn't support this functionality natively, but there are some possible workarounds:

• Use Make for recipes which would benefit from incremental compilation (you could call these recipes from Just, so you don't need to remember which recipes use Make and which use Just)

• Write a recipe that uses entr or cargo-watch to re-run a recipe when a file changes. This isn't quite what you asked for, but would be a way to at least only rerun a build command when something changes.

[runeimp]

@Jumblemuddle you might use a tool like chkfilehash in https://github.com/leonidessaguisagjr/filehash. I played with it a bit and you can do something like

$ pip install filehash

build src='source.rs':
	#!/bin/sh
	if [[ $(chkfilehash -c {{src}}.sha256 | grep OK) -eq 0 ]]; then
		echo "No changes to rebuild"
		exit 0
	fi
	chkfilehash {{src}} > {{src}}.sha256
	echo "We will rebuild!"

This requires you have Python installed already. But I'm sure there are other tools available as well. Actually makes me want to make a simple tool in Go for a tool supported on many platforms without any dependencies. 😃

[garrett-hopper]

Thanks, @casey and @runeimp, these are great suggestions.

[runeimp]

@Jumblemuddle check out https://github.com/runeimp/filedelta if you like. 😃

[garrett-hopper]

Looks great, @runeimp! :)