Rename worktree crate to project, pull in Project

Also, move the high-level fuzzy mathcing functions in
zed::fuzzy into the fuzzy crate so that project can
use them.

This required defining a 'PathMatchCandidateSet' trait
to avoid a circular dependency from fuzzy to worktree.

Co-Authored-By: Nathan Sobo <nathan@zed.dev>

crates/project/src/ignore.rs

@@ -0,0 +1,57 @@
+use ignore::gitignore::Gitignore;
+use std::{ffi::OsStr, path::Path, sync::Arc};
+
+pub enum IgnoreStack {
+    None,
+    Some {
+        base: Arc<Path>,
+        ignore: Arc<Gitignore>,
+        parent: Arc<IgnoreStack>,
+    },
+    All,
+}
+
+impl IgnoreStack {
+    pub fn none() -> Arc<Self> {
+        Arc::new(Self::None)
+    }
+
+    pub fn all() -> Arc<Self> {
+        Arc::new(Self::All)
+    }
+
+    pub fn is_all(&self) -> bool {
+        matches!(self, IgnoreStack::All)
+    }
+
+    pub fn append(self: Arc<Self>, base: Arc<Path>, ignore: Arc<Gitignore>) -> Arc<Self> {
+        match self.as_ref() {
+            IgnoreStack::All => self,
+            _ => Arc::new(Self::Some {
+                base,
+                ignore,
+                parent: self,
+            }),
+        }
+    }
+
+    pub fn is_path_ignored(&self, path: &Path, is_dir: bool) -> bool {
+        if is_dir && path.file_name() == Some(OsStr::new(".git")) {
+            return true;
+        }
+
+        match self {
+            Self::None => false,
+            Self::All => true,
+            Self::Some {
+                base,
+                ignore,
+                parent: prev,
+            } => match ignore.matched(path.strip_prefix(base).unwrap(), is_dir) {
+                ignore::Match::None => prev.is_path_ignored(path, is_dir),
+                ignore::Match::Ignore(_) => true,
+                ignore::Match::Whitelist(_) => false,
+            },
+        }
+    }
+}