Display warnings if certain well-known directories (e.g. .git) are imported

[Profpatsch]

Lorri should make an effort to help the user prevent common mistakes, by displaying (silence-able?) warnings.

• .git directories
• Directories that are very large

In another step, if we know what kind of project the user has, we can check for language-specific directories (e.g. target/ for Rust/cargo projects). Or even implement that logic for them with our own library of mkShell-like functions (lorriRustProject, lorriGoProject …).

This is a step towards #84

[Profpatsch]

A first step is to collect a series of directories which should be linted.

An idea is to use .gitignore to find ignored files and print a warning if one of those is added to the watcher.

New files are currently added here:

lorri/src/ops/daemon.rs

Lines 60 to 72 in ae95c4d

	pool.spawn("build-instruction-handler", move || {
	// For each build instruction, add the corresponding file
	// to the watch list.
	for start_build in accept_messages_rx {
	let project = ::project::Project::new(
	start_build.nix_file,
	paths.gc_root_dir(),
	paths.cas_store().clone(),
	)
	// TODO: the project needs to create its gc root dir
	.unwrap();
	daemon.add(project)
	}

so that’s the place where the linter should hook into.

[0mbi]

I take that one.

[0mbi]

First draft PR, looking for your comments.

Next steps would be:

• add cli flag to add some file like .gitignore and add the regexps from it.