Rename vfs -> memofs across the codebase

memofs/src/snapshot.rs

@@ -0,0 +1,44 @@
+use std::collections::BTreeMap;
+
+/// A slice of a tree of files. Can be loaded into an
+/// [`InMemoryFs`](struct.InMemoryFs.html).
+#[derive(Debug)]
+#[non_exhaustive]
+pub enum VfsSnapshot {
+    File {
+        contents: Vec<u8>,
+    },
+
+    Dir {
+        children: BTreeMap<String, VfsSnapshot>,
+    },
+}
+
+impl VfsSnapshot {
+    pub fn file<C: Into<Vec<u8>>>(contents: C) -> Self {
+        Self::File {
+            contents: contents.into(),
+        }
+    }
+
+    pub fn dir<K: Into<String>, I: IntoIterator<Item = (K, VfsSnapshot)>>(children: I) -> Self {
+        Self::Dir {
+            children: children
+                .into_iter()
+                .map(|(key, value)| (key.into(), value))
+                .collect(),
+        }
+    }
+
+    pub fn empty_file() -> Self {
+        Self::File {
+            contents: Vec::new(),
+        }
+    }
+
+    pub fn empty_dir() -> Self {
+        Self::Dir {
+            children: BTreeMap::new(),
+        }
+    }
+}