Refactor: Extract new crate binstalk-registry (#1289)

To speedup codegen of `binstalk` and enable it to be reused.

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

crates/binstalk-registry/src/vfs.rs

@@ -0,0 +1,43 @@
+use std::{
+    collections::{hash_set::HashSet, BTreeMap},
+    io,
+    path::Path,
+};
+
+use cargo_toml_workspace::cargo_toml::AbstractFilesystem;
+use normalize_path::NormalizePath;
+
+/// This type stores the filesystem structure for the crate tarball
+/// extracted in memory and can be passed to
+/// `cargo_toml::Manifest::complete_from_abstract_filesystem`.
+#[derive(Debug, Default)]
+pub(super) struct Vfs(BTreeMap<Box<Path>, HashSet<Box<str>>>);
+
+impl Vfs {
+    /// * `path` - must be canonical, must not be empty.
+    pub(super) fn add_path(&mut self, mut path: &Path) {
+        while let Some(parent) = path.parent() {
+            // Since path has parent, it must have a filename
+            let filename = path.file_name().unwrap();
+
+            // `cargo_toml`'s implementation does the same thing.
+            // https://docs.rs/cargo_toml/0.11.5/src/cargo_toml/afs.rs.html#24
+            let filename = filename.to_string_lossy();
+
+            self.0
+                .entry(parent.into())
+                .or_insert_with(|| HashSet::with_capacity(4))
+                .insert(filename.into());
+
+            path = parent;
+        }
+    }
+}
+
+impl AbstractFilesystem for Vfs {
+    fn file_names_in(&self, rel_path: &str) -> io::Result<HashSet<Box<str>>> {
+        let rel_path = Path::new(rel_path).normalize();
+
+        Ok(self.0.get(&*rel_path).map(Clone::clone).unwrap_or_default())
+    }
+}