Git improvements (#24238)

- **Base diffs on uncommitted changes**
- **Show added files in project diff view**
- **Fix git panel optimism**

Release Notes:

- Git: update diffs to be relative to HEAD instead of the index; to pave
the way for showing which hunks are staged

---------

Co-authored-by: Cole <cole@zed.dev>

crates/multi_buffer/src/multi_buffer.rs

@@ -67,7 +67,7 @@ pub struct MultiBuffer {
     /// Contains the state of the buffers being edited
     buffers: RefCell<HashMap<BufferId, BufferState>>,
     // only used by consumers using `set_excerpts_for_buffer`
-    buffers_by_path: BTreeMap<Arc<Path>, Vec<ExcerptId>>,
+    buffers_by_path: BTreeMap<PathKey, Vec<ExcerptId>>,
     diff_bases: HashMap<BufferId, ChangeSetState>,
     all_diff_hunks_expanded: bool,
     subscriptions: Topic,
@@ -143,6 +143,15 @@ impl MultiBufferDiffHunk {
     }
 }
 
+#[derive(PartialEq, Eq, Ord, PartialOrd, Clone, Hash, Debug)]
+pub struct PathKey(String);
+
+impl PathKey {
+    pub fn namespaced(namespace: &str, path: &Path) -> Self {
+        Self(format!("{}/{}", namespace, path.to_string_lossy()))
+    }
+}
+
 pub type MultiBufferPoint = Point;
 type ExcerptOffset = TypedOffset<Excerpt>;
 type ExcerptPoint = TypedPoint<Excerpt>;
@@ -1395,7 +1404,7 @@ impl MultiBuffer {
         anchor_ranges
     }
 
-    pub fn location_for_path(&self, path: &Arc<Path>, cx: &App) -> Option<Anchor> {
+    pub fn location_for_path(&self, path: &PathKey, cx: &App) -> Option<Anchor> {
         let excerpt_id = self.buffers_by_path.get(path)?.first()?;
         let snapshot = self.snapshot(cx);
         let excerpt = snapshot.excerpt(*excerpt_id)?;
@@ -1408,7 +1417,7 @@ impl MultiBuffer {
 
     pub fn set_excerpts_for_path(
         &mut self,
-        path: Arc<Path>,
+        path: PathKey,
         buffer: Entity<Buffer>,
         ranges: Vec<Range<Point>>,
         context_line_count: u32,
@@ -1517,11 +1526,11 @@ impl MultiBuffer {
         }
     }
 
-    pub fn paths(&self) -> impl Iterator<Item = Arc<Path>> + '_ {
+    pub fn paths(&self) -> impl Iterator<Item = PathKey> + '_ {
         self.buffers_by_path.keys().cloned()
     }
 
-    pub fn remove_excerpts_for_path(&mut self, path: Arc<Path>, cx: &mut Context<Self>) {
+    pub fn remove_excerpts_for_path(&mut self, path: PathKey, cx: &mut Context<Self>) {
         if let Some(to_remove) = self.buffers_by_path.remove(&path) {
             self.remove_excerpts(to_remove, cx)
         }

crates/multi_buffer/src/multi_buffer_tests.rs

@@ -6,7 +6,7 @@ use language::{Buffer, Rope};
 use parking_lot::RwLock;
 use rand::prelude::*;
 use settings::SettingsStore;
-use std::{env, path::PathBuf};
+use std::env;
 use util::test::sample_text;
 
 #[ctor::ctor]
@@ -1596,7 +1596,7 @@ fn test_set_excerpts_for_buffer(cx: &mut TestAppContext) {
             cx,
         )
     });
-    let path1: Arc<Path> = Arc::from(PathBuf::from("path1"));
+    let path1: PathKey = PathKey::namespaced("0", Path::new("/"));
     let buf2 = cx.new(|cx| {
         Buffer::local(
             indoc! {
@@ -1615,7 +1615,7 @@ fn test_set_excerpts_for_buffer(cx: &mut TestAppContext) {
             cx,
         )
     });
-    let path2: Arc<Path> = Arc::from(PathBuf::from("path2"));
+    let path2 = PathKey::namespaced("x", Path::new("/"));
 
     let multibuffer = cx.new(|_| MultiBuffer::new(Capability::ReadWrite));
     multibuffer.update(cx, |multibuffer, cx| {