Add global Fs instance (#15044)

This PR adds a global `Fs` instance to the app context.

This will make it easier to access the filesystem in some cases instead
of having to thread it around.

Release Notes:

- N/A

crates/fs/Cargo.toml

@@ -19,7 +19,7 @@ collections.workspace = true
 futures.workspace = true
 git.workspace = true
 git2.workspace = true
-gpui = { workspace = true, optional = true }
+gpui.workspace = true
 lazy_static.workspace = true
 libc.workspace = true
 parking_lot.workspace = true

crates/fs/src/fs.rs

@@ -12,6 +12,7 @@ use std::os::unix::fs::MetadataExt;
 use async_tar::Archive;
 use futures::{future::BoxFuture, AsyncRead, Stream, StreamExt};
 use git::repository::{GitRepository, RealGitRepository};
+use gpui::{AppContext, Global, ReadGlobal};
 use rope::Rope;
 use smol::io::AsyncWriteExt;
 use std::{
@@ -102,6 +103,22 @@ pub trait Fs: Send + Sync {
     }
 }
 
+struct GlobalFs(Arc<dyn Fs>);
+
+impl Global for GlobalFs {}
+
+impl dyn Fs {
+    /// Returns the global [`Fs`].
+    pub fn global(cx: &AppContext) -> Arc<Self> {
+        GlobalFs::global(cx).0.clone()
+    }
+
+    /// Sets the global [`Fs`].
+    pub fn set_global(fs: Arc<Self>, cx: &mut AppContext) {
+        cx.set_global(GlobalFs(fs));
+    }
+}
+
 #[derive(Copy, Clone, Default)]
 pub struct CreateOptions {
     pub overwrite: bool,