Move actual include logic to ProjectRoot

This way the two IncludeRustFiles implementations can simply call the
ProjectRoots' methods, so that the include logic is in one place.

crates/ra_project_model/src/lib.rs

@@ -15,6 +15,8 @@ use ra_db::{CrateGraph, FileId, Edition};
 
 use serde_json::from_reader;
 
+use relative_path::RelativePath;
+
 pub use crate::{
     cargo_workspace::{CargoWorkspace, Package, Target, TargetKind},
     json_project::JsonProject,
@@ -43,17 +45,39 @@ pub struct ProjectRoot {
 }
 
 impl ProjectRoot {
-    fn new(path: PathBuf, is_member: bool) -> ProjectRoot {
+    pub fn new(path: PathBuf, is_member: bool) -> ProjectRoot {
         ProjectRoot { path, is_member }
     }
 
-    pub fn into_path(self) -> PathBuf {
-        self.path
+    pub fn path(&self) -> &PathBuf {
+        &self.path
     }
 
     pub fn is_member(&self) -> bool {
         self.is_member
     }
+
+    pub fn include_dir(&self, dir_path: &RelativePath) -> bool {
+        const COMMON_IGNORED_DIRS: &[&str] = &["node_modules", "target", ".git"];
+        const EXTERNAL_IGNORED_DIRS: &[&str] = &["examples", "tests", "benches"];
+
+        let is_ignored = if self.is_member {
+            dir_path.components().any(|c| COMMON_IGNORED_DIRS.contains(&c.as_str()))
+        } else {
+            dir_path.components().any(|c| {
+                let path = c.as_str();
+                COMMON_IGNORED_DIRS.contains(&path) || EXTERNAL_IGNORED_DIRS.contains(&path)
+            })
+        };
+
+        let hidden = dir_path.components().any(|c| c.as_str().starts_with("."));
+
+        !is_ignored && !hidden
+    }
+
+    pub fn include_file(&self, file_path: &RelativePath) -> bool {
+        file_path.extension() == Some("rs")
+    }
 }
 
 impl ProjectWorkspace {