refactor: Introduce crates folder (#2088)

This PR introduces a new `crates` directory and moves all "product" crates into that folder. 

Part of #2059.

crates/ruff_cli/src/resolve.rs

@@ -0,0 +1,68 @@
+use std::path::Path;
+
+use anyhow::Result;
+use path_absolutize::path_dedot;
+use ruff::resolver::{
+    resolve_settings_with_processor, ConfigProcessor, PyprojectDiscovery, Relativity,
+};
+use ruff::settings::configuration::Configuration;
+use ruff::settings::{pyproject, AllSettings};
+
+use crate::args::Overrides;
+
+/// Resolve the relevant settings strategy and defaults for the current
+/// invocation.
+pub fn resolve(
+    isolated: bool,
+    config: Option<&Path>,
+    overrides: &Overrides,
+    stdin_filename: Option<&Path>,
+) -> Result<PyprojectDiscovery> {
+    // First priority: if we're running in isolated mode, use the default settings.
+    if isolated {
+        let mut config = Configuration::default();
+        overrides.process_config(&mut config);
+        let settings = AllSettings::from_configuration(config, &path_dedot::CWD)?;
+        return Ok(PyprojectDiscovery::Fixed(settings));
+    }
+
+    // Second priority: the user specified a `pyproject.toml` file. Use that
+    // `pyproject.toml` for _all_ configuration, and resolve paths relative to the
+    // current working directory. (This matches ESLint's behavior.)
+    if let Some(pyproject) = config {
+        let settings = resolve_settings_with_processor(pyproject, &Relativity::Cwd, overrides)?;
+        return Ok(PyprojectDiscovery::Fixed(settings));
+    }
+
+    // Third priority: find a `pyproject.toml` file in either an ancestor of
+    // `stdin_filename` (if set) or the current working path all paths relative to
+    // that directory. (With `Strategy::Hierarchical`, we'll end up finding
+    // the "closest" `pyproject.toml` file for every Python file later on,
+    // so these act as the "default" settings.)
+    if let Some(pyproject) = pyproject::find_settings_toml(
+        stdin_filename
+            .as_ref()
+            .unwrap_or(&path_dedot::CWD.as_path()),
+    )? {
+        let settings = resolve_settings_with_processor(&pyproject, &Relativity::Parent, overrides)?;
+        return Ok(PyprojectDiscovery::Hierarchical(settings));
+    }
+
+    // Fourth priority: find a user-specific `pyproject.toml`, but resolve all paths
+    // relative the current working directory. (With `Strategy::Hierarchical`, we'll
+    // end up the "closest" `pyproject.toml` file for every Python file later on, so
+    // these act as the "default" settings.)
+    if let Some(pyproject) = pyproject::find_user_settings_toml() {
+        let settings = resolve_settings_with_processor(&pyproject, &Relativity::Cwd, overrides)?;
+        return Ok(PyprojectDiscovery::Hierarchical(settings));
+    }
+
+    // Fallback: load Ruff's default settings, and resolve all paths relative to the
+    // current working directory. (With `Strategy::Hierarchical`, we'll end up the
+    // "closest" `pyproject.toml` file for every Python file later on, so these act
+    // as the "default" settings.)
+    let mut config = Configuration::default();
+    overrides.process_config(&mut config);
+    let settings = AllSettings::from_configuration(config, &path_dedot::CWD)?;
+    Ok(PyprojectDiscovery::Hierarchical(settings))
+}