Track if tasks are up-to-date based on file timestamps or checksums

[Nezteb]

Task/taskfile supports several ways of preventing unncessary work, one of which is by fingerprinting locally generated files and their sources.

If just could support this in some capacity, I think it'd help improve just's user experience. 😄

[laniakea64]

While waiting for just dev to respond, here's a possible workaround example: a recipe foo that only needs to run if files a.txt and b.txt have different checksums since last run -

foo:
	#!/bin/bash
	job=foo
	sha256sums={{quote(justfile_directory() / '.sha256sums-') + '"$job"'}}
	dependencies='a.txt b.txt'
	if [[ -f "$sha256sums" ]] && sha256sum --status -c "$sha256sums" ;then
	  echo "Job '$job' is up-to-date"
	  exit 0
	fi
	sha256sum $dependencies > "$sha256sums"
	echo "Running job '$job'..."

(This example assumes files a.txt and b.txt always exist.)

[casey]

I think this is a dupe of #867, have a look.

[qtfkwk]

I created https://crates.io/crates/mkrs primarily for this reason (and to write the Makefile in markdown); it seems like the same approach may not fit in just's design. Mkrs distinguishes between file and non-file targets, and runs the recipe for a file target if -B (force processing), file does not exist, or is outdated (any of target's source files are newer than the target file). Please feel free to use as it as a reference. Thanks!