diff --git a/Cargo.lock b/Cargo.lock
index 3c87f336de..75dd5530c9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1031,6 +1031,7 @@ dependencies = [
  "env_logger",
  "envy",
  "futures",
+ "git",
  "gpui",
  "hyper",
  "language",
@@ -1061,6 +1062,7 @@ dependencies = [
  "tracing",
  "tracing-log",
  "tracing-subscriber",
+ "unindent",
  "util",
  "workspace",
 ]
@@ -2232,6 +2234,7 @@ dependencies = [
  "anyhow",
  "async-trait",
  "clock",
+ "collections",
  "git2",
  "lazy_static",
  "log",
diff --git a/crates/collab/Cargo.toml b/crates/collab/Cargo.toml
index 9b3603e6e4..47c86e0fe7 100644
--- a/crates/collab/Cargo.toml
+++ b/crates/collab/Cargo.toml
@@ -1,5 +1,5 @@
 [package]
-authors = ["Nathan Sobo <nathan@warp.dev>"]
+authors = ["Nathan Sobo <nathan@zed.dev>"]
 default-run = "collab"
 edition = "2021"
 name = "collab"
@@ -26,6 +26,7 @@ base64 = "0.13"
 clap = { version = "3.1", features = ["derive"], optional = true }
 envy = "0.4.2"
 futures = "0.3"
+git = { path = "../git" }
 hyper = "0.14"
 lazy_static = "1.4"
 lipsum = { version = "0.8", optional = true }
@@ -65,11 +66,13 @@ project = { path = "../project", features = ["test-support"] }
 settings = { path = "../settings", features = ["test-support"] }
 theme = { path = "../theme" }
 workspace = { path = "../workspace", features = ["test-support"] }
+git = { path = "../git", features = ["test-support"] }
 ctor = "0.1"
 env_logger = "0.9"
 util = { path = "../util" }
 lazy_static = "1.4"
 serde_json = { version = "1.0", features = ["preserve_order"] }
+unindent = "0.1"
 
 [features]
 seed-support = ["clap", "lipsum", "reqwest"]
diff --git a/crates/collab/src/integration_tests.rs b/crates/collab/src/integration_tests.rs
index 3c9886dc16..586d988ef1 100644
--- a/crates/collab/src/integration_tests.rs
+++ b/crates/collab/src/integration_tests.rs
@@ -51,6 +51,7 @@ use std::{
     time::Duration,
 };
 use theme::ThemeRegistry;
+use unindent::Unindent as _;
 use workspace::{Item, SplitDirection, ToggleFollow, Workspace};
 
 #[ctor::ctor]
@@ -946,6 +947,143 @@ async fn test_propagate_saves_and_fs_changes(
         .await;
 }
 
+#[gpui::test(iterations = 10)]
+async fn test_git_head_text(
+    executor: Arc<Deterministic>,
+    cx_a: &mut TestAppContext,
+    cx_b: &mut TestAppContext,
+) {
+    executor.forbid_parking();
+    let mut server = TestServer::start(cx_a.foreground(), cx_a.background()).await;
+    let client_a = server.create_client(cx_a, "user_a").await;
+    let client_b = server.create_client(cx_b, "user_b").await;
+    server
+        .make_contacts(vec![(&client_a, cx_a), (&client_b, cx_b)])
+        .await;
+
+    client_a
+        .fs
+        .insert_tree(
+            "/dir",
+            json!({
+            ".git": {},
+            "a.txt": "
+                    one
+                    two
+                    three
+                ".unindent(),
+            }),
+        )
+        .await;
+
+    let head_text = "
+        one
+        three
+    "
+    .unindent();
+
+    let new_head_text = "
+        1
+        two
+        three
+    "
+    .unindent();
+
+    client_a
+        .fs
+        .as_fake()
+        .set_head_state_for_git_repository(
+            Path::new("/dir/.git"),
+            &[(Path::new("a.txt"), head_text.clone())],
+        )
+        .await;
+
+    let (project_a, worktree_id) = client_a.build_local_project("/dir", cx_a).await;
+    let project_b = client_b.build_remote_project(&project_a, cx_a, cx_b).await;
+
+    // Create the buffer
+    let buffer_a = project_a
+        .update(cx_a, |p, cx| p.open_buffer((worktree_id, "/dir/a.txt"), cx))
+        .await
+        .unwrap();
+
+    // Wait for it to catch up to the new diff
+    buffer_a
+        .condition(cx_a, |buffer, _| !buffer.is_recalculating_git_diff())
+        .await;
+
+    // Smoke test diffing
+    buffer_a.read_with(cx_a, |buffer, _| {
+        assert_eq!(buffer.head_text(), Some(head_text.as_ref()));
+        git::diff::assert_hunks(
+            buffer.snapshot().git_diff_hunks_in_range(0..4),
+            &buffer,
+            &head_text,
+            &[(1..2, "", "two\n")],
+        );
+    });
+
+    // Create remote buffer
+    let buffer_b = project_b
+        .update(cx_b, |p, cx| p.open_buffer((worktree_id, "/dir/a.txt"), cx))
+        .await
+        .unwrap();
+
+    //TODO: WAIT FOR REMOTE UPDATES TO FINISH
+
+    // Smoke test diffing
+    buffer_b.read_with(cx_b, |buffer, _| {
+        assert_eq!(buffer.head_text(), Some(head_text.as_ref()));
+        git::diff::assert_hunks(
+            buffer.snapshot().git_diff_hunks_in_range(0..4),
+            &buffer,
+            &head_text,
+            &[(1..2, "", "two\n")],
+        );
+    });
+
+    // TODO: Create a dummy file event
+    client_a
+        .fs
+        .as_fake()
+        .set_head_state_for_git_repository(
+            Path::new("/dir/.git"),
+            &[(Path::new("a.txt"), new_head_text.clone())],
+        )
+        .await;
+
+    // TODO: Flush this file event
+
+    // Wait for buffer_a to receive it
+    buffer_a
+        .condition(cx_a, |buffer, _| !buffer.is_recalculating_git_diff())
+        .await;
+
+    // Smoke test new diffing
+    buffer_a.read_with(cx_a, |buffer, _| {
+        assert_eq!(buffer.head_text(), Some(new_head_text.as_ref()));
+        git::diff::assert_hunks(
+            buffer.snapshot().git_diff_hunks_in_range(0..4),
+            &buffer,
+            &head_text,
+            &[(0..1, "1", "one\n")],
+        );
+    });
+
+    //TODO: WAIT FOR REMOTE UPDATES TO FINISH on B
+
+    // Smoke test B
+    buffer_b.read_with(cx_b, |buffer, _| {
+        assert_eq!(buffer.head_text(), Some(new_head_text.as_ref()));
+        git::diff::assert_hunks(
+            buffer.snapshot().git_diff_hunks_in_range(0..4),
+            &buffer,
+            &head_text,
+            &[(0..1, "1", "one\n")],
+        );
+    });
+}
+
 #[gpui::test(iterations = 10)]
 async fn test_fs_operations(
     executor: Arc<Deterministic>,
diff --git a/crates/git/Cargo.toml b/crates/git/Cargo.toml
index 7ef9a953ba..744fdc8b99 100644
--- a/crates/git/Cargo.toml
+++ b/crates/git/Cargo.toml
@@ -13,12 +13,15 @@ git2 = { version = "0.15", default-features = false }
 lazy_static = "1.4.0"
 sum_tree = { path = "../sum_tree" }
 text = { path = "../text" }
+collections = { path = "../collections" }
 util = { path = "../util" }
 log = { version = "0.4.16", features = ["kv_unstable_serde"] }
 smol = "1.2"
 parking_lot = "0.11.1"
 async-trait = "0.1"
 
-
 [dev-dependencies]
 unindent = "0.1.7"
+
+[features]
+test-support = []
diff --git a/crates/git/src/diff.rs b/crates/git/src/diff.rs
index 4d12ca90d1..6c904d44d1 100644
--- a/crates/git/src/diff.rs
+++ b/crates/git/src/diff.rs
@@ -222,6 +222,40 @@ impl BufferDiff {
     }
 }
 
+/// Range (crossing new lines), old, new
+#[cfg(any(test, feature = "test-support"))]
+#[track_caller]
+pub fn assert_hunks<Iter>(
+    diff_hunks: Iter,
+    buffer: &BufferSnapshot,
+    head_text: &str,
+    expected_hunks: &[(Range<u32>, &str, &str)],
+) where
+    Iter: Iterator<Item = DiffHunk<u32>>,
+{
+    let actual_hunks = diff_hunks
+        .map(|hunk| {
+            (
+                hunk.buffer_range.clone(),
+                &head_text[hunk.head_byte_range],
+                buffer
+                    .text_for_range(
+                        Point::new(hunk.buffer_range.start, 0)
+                            ..Point::new(hunk.buffer_range.end, 0),
+                    )
+                    .collect::<String>(),
+            )
+        })
+        .collect::<Vec<_>>();
+
+    let expected_hunks: Vec<_> = expected_hunks
+        .iter()
+        .map(|(r, s, h)| (r.clone(), *s, h.to_string()))
+        .collect();
+
+    assert_eq!(actual_hunks, expected_hunks);
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -248,21 +282,19 @@ mod tests {
         let mut diff = BufferDiff::new();
         smol::block_on(diff.update(&head_text, &buffer));
         assert_hunks(
-            &diff,
+            diff.hunks(&buffer),
             &buffer,
             &head_text,
             &[(1..2, "two\n", "HELLO\n")],
-            None,
         );
 
         buffer.edit([(0..0, "point five\n")]);
         smol::block_on(diff.update(&head_text, &buffer));
         assert_hunks(
-            &diff,
+            diff.hunks(&buffer),
             &buffer,
             &head_text,
             &[(0..1, "", "point five\n"), (2..3, "two\n", "HELLO\n")],
-            None,
         );
     }
 
@@ -309,7 +341,7 @@ mod tests {
         assert_eq!(diff.hunks(&buffer).count(), 8);
 
         assert_hunks(
-            &diff,
+            diff.hunks_in_range(7..12, &buffer),
             &buffer,
             &head_text,
             &[
@@ -317,39 +349,6 @@ mod tests {
                 (9..10, "six\n", "SIXTEEN\n"),
                 (12..13, "", "WORLD\n"),
             ],
-            Some(7..12),
         );
     }
-
-    #[track_caller]
-    fn assert_hunks(
-        diff: &BufferDiff,
-        buffer: &BufferSnapshot,
-        head_text: &str,
-        expected_hunks: &[(Range<u32>, &str, &str)],
-        range: Option<Range<u32>>,
-    ) {
-        let actual_hunks = diff
-            .hunks_in_range(range.unwrap_or(0..u32::MAX), buffer)
-            .map(|hunk| {
-                (
-                    hunk.buffer_range.clone(),
-                    &head_text[hunk.head_byte_range],
-                    buffer
-                        .text_for_range(
-                            Point::new(hunk.buffer_range.start, 0)
-                                ..Point::new(hunk.buffer_range.end, 0),
-                        )
-                        .collect::<String>(),
-                )
-            })
-            .collect::<Vec<_>>();
-
-        let expected_hunks: Vec<_> = expected_hunks
-            .iter()
-            .map(|(r, s, h)| (r.clone(), *s, h.to_string()))
-            .collect();
-
-        assert_eq!(actual_hunks, expected_hunks);
-    }
 }
diff --git a/crates/git/src/repository.rs b/crates/git/src/repository.rs
index f834ebc219..fb43e44561 100644
--- a/crates/git/src/repository.rs
+++ b/crates/git/src/repository.rs
@@ -1,7 +1,11 @@
 use anyhow::Result;
+use collections::HashMap;
 use git2::Repository as LibGitRepository;
 use parking_lot::Mutex;
-use std::{path::Path, sync::Arc};
+use std::{
+    path::{Path, PathBuf},
+    sync::Arc,
+};
 use util::ResultExt;
 
 #[async_trait::async_trait]
@@ -140,14 +144,25 @@ pub struct FakeGitRepository {
     content_path: Arc<Path>,
     git_dir_path: Arc<Path>,
     scan_id: usize,
+    state: Arc<Mutex<FakeGitRepositoryState>>,
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct FakeGitRepositoryState {
+    pub index_contents: HashMap<PathBuf, String>,
 }
 
 impl FakeGitRepository {
-    pub fn open(dotgit_path: &Path, scan_id: usize) -> Box<dyn GitRepository> {
+    pub fn open(
+        dotgit_path: &Path,
+        scan_id: usize,
+        state: Arc<Mutex<FakeGitRepositoryState>>,
+    ) -> Box<dyn GitRepository> {
         Box::new(FakeGitRepository {
             content_path: dotgit_path.parent().unwrap().into(),
             git_dir_path: dotgit_path.into(),
             scan_id,
+            state,
         })
     }
 }
@@ -174,12 +189,13 @@ impl GitRepository for FakeGitRepository {
         self.scan_id
     }
 
-    async fn load_head_text(&self, _: &Path) -> Option<String> {
-        None
+    async fn load_head_text(&self, path: &Path) -> Option<String> {
+        let state = self.state.lock();
+        state.index_contents.get(path).cloned()
     }
 
     fn reopen_git_repo(&mut self) -> bool {
-        false
+        true
     }
 
     fn git_repo(&self) -> Arc<Mutex<LibGitRepository>> {
diff --git a/crates/language/src/buffer.rs b/crates/language/src/buffer.rs
index 0268f1cc68..831236ad5d 100644
--- a/crates/language/src/buffer.rs
+++ b/crates/language/src/buffer.rs
@@ -662,6 +662,11 @@ impl Buffer {
         task
     }
 
+    #[cfg(any(test, feature = "test-support"))]
+    pub fn head_text(&self) -> Option<&str> {
+        self.head_text.as_deref()
+    }
+
     pub fn update_head_text(&mut self, head_text: Option<String>, cx: &mut ModelContext<Self>) {
         self.head_text = head_text;
         self.git_diff_recalc(cx);
@@ -671,6 +676,10 @@ impl Buffer {
         self.git_diff_status.diff.needs_update(self)
     }
 
+    pub fn is_recalculating_git_diff(&self) -> bool {
+        self.git_diff_status.update_in_progress
+    }
+
     pub fn git_diff_recalc(&mut self, cx: &mut ModelContext<Self>) {
         if self.git_diff_status.update_in_progress {
             self.git_diff_status.update_requested = true;
diff --git a/crates/project/src/fs.rs b/crates/project/src/fs.rs
index c14edcd5e4..2b914ae373 100644
--- a/crates/project/src/fs.rs
+++ b/crates/project/src/fs.rs
@@ -1,7 +1,7 @@
 use anyhow::{anyhow, Result};
 use fsevent::EventStream;
 use futures::{future::BoxFuture, Stream, StreamExt};
-use git::repository::{GitRepository, RealGitRepository};
+use git::repository::{FakeGitRepositoryState, GitRepository, RealGitRepository};
 use language::LineEnding;
 use smol::io::{AsyncReadExt, AsyncWriteExt};
 use std::{
@@ -277,6 +277,7 @@ enum FakeFsEntry {
         inode: u64,
         mtime: SystemTime,
         entries: BTreeMap<String, Arc<Mutex<FakeFsEntry>>>,
+        git_repo_state: Option<Arc<parking_lot::Mutex<git::repository::FakeGitRepositoryState>>>,
     },
     Symlink {
         target: PathBuf,
@@ -391,6 +392,7 @@ impl FakeFs {
                     inode: 0,
                     mtime: SystemTime::now(),
                     entries: Default::default(),
+                    git_repo_state: None,
                 })),
                 next_inode: 1,
                 event_txs: Default::default(),
@@ -480,6 +482,31 @@ impl FakeFs {
         .boxed()
     }
 
+    pub async fn set_head_state_for_git_repository(
+        &self,
+        dot_git: &Path,
+        head_state: &[(&Path, String)],
+    ) {
+        let content_path = dot_git.parent().unwrap();
+        let state = self.state.lock().await;
+        let entry = state.read_path(dot_git).await.unwrap();
+        let mut entry = entry.lock().await;
+
+        if let FakeFsEntry::Dir { git_repo_state, .. } = &mut *entry {
+            let repo_state = git_repo_state.get_or_insert_with(Default::default);
+            let mut repo_state = repo_state.lock();
+
+            repo_state.index_contents.clear();
+            repo_state.index_contents.extend(
+                head_state
+                    .iter()
+                    .map(|(path, content)| (content_path.join(path), content.clone())),
+            );
+        } else {
+            panic!("not a directory");
+        }
+    }
+
     pub async fn files(&self) -> Vec<PathBuf> {
         let mut result = Vec::new();
         let mut queue = collections::VecDeque::new();
@@ -569,6 +596,7 @@ impl Fs for FakeFs {
                             inode,
                             mtime: SystemTime::now(),
                             entries: Default::default(),
+                            git_repo_state: None,
                         }))
                     });
                     Ok(())
@@ -854,10 +882,26 @@ impl Fs for FakeFs {
     }
 
     fn open_repo(&self, abs_dot_git: &Path) -> Option<Box<dyn GitRepository>> {
-        Some(git::repository::FakeGitRepository::open(
-            abs_dot_git.into(),
-            0,
-        ))
+        let executor = self.executor.upgrade().unwrap();
+        executor.block(async move {
+            let state = self.state.lock().await;
+            let entry = state.read_path(abs_dot_git).await.unwrap();
+            let mut entry = entry.lock().await;
+            if let FakeFsEntry::Dir { git_repo_state, .. } = &mut *entry {
+                let state = git_repo_state
+                    .get_or_insert_with(|| {
+                        Arc::new(parking_lot::Mutex::new(FakeGitRepositoryState::default()))
+                    })
+                    .clone();
+                Some(git::repository::FakeGitRepository::open(
+                    abs_dot_git.into(),
+                    0,
+                    state,
+                ))
+            } else {
+                None
+            }
+        })
     }
 
     fn is_fake(&self) -> bool {
diff --git a/crates/project/src/worktree.rs b/crates/project/src/worktree.rs
index 0d2594475c..d3a5f710e0 100644
--- a/crates/project/src/worktree.rs
+++ b/crates/project/src/worktree.rs
@@ -3288,15 +3288,15 @@ mod tests {
     #[test]
     fn test_changed_repos() {
         let prev_repos: Vec<Box<dyn GitRepository>> = vec![
-            FakeGitRepository::open(Path::new("/.git"), 0),
-            FakeGitRepository::open(Path::new("/a/.git"), 0),
-            FakeGitRepository::open(Path::new("/a/b/.git"), 0),
+            FakeGitRepository::open(Path::new("/.git"), 0, Default::default()),
+            FakeGitRepository::open(Path::new("/a/.git"), 0, Default::default()),
+            FakeGitRepository::open(Path::new("/a/b/.git"), 0, Default::default()),
         ];
 
         let new_repos: Vec<Box<dyn GitRepository>> = vec![
-            FakeGitRepository::open(Path::new("/a/.git"), 1),
-            FakeGitRepository::open(Path::new("/a/b/.git"), 0),
-            FakeGitRepository::open(Path::new("/a/c/.git"), 0),
+            FakeGitRepository::open(Path::new("/a/.git"), 1, Default::default()),
+            FakeGitRepository::open(Path::new("/a/b/.git"), 0, Default::default()),
+            FakeGitRepository::open(Path::new("/a/c/.git"), 0, Default::default()),
         ];
 
         let res = LocalWorktree::changed_repos(&prev_repos, &new_repos);
diff --git a/crates/text/src/anchor.rs b/crates/text/src/anchor.rs
index ab0e1eeabc..9f70ae1cc7 100644
--- a/crates/text/src/anchor.rs
+++ b/crates/text/src/anchor.rs
@@ -26,7 +26,7 @@ impl Anchor {
         bias: Bias::Right,
         buffer_id: None,
     };
-    
+
     pub fn cmp(&self, other: &Anchor, buffer: &BufferSnapshot) -> Ordering {
         let fragment_id_comparison = if self.timestamp == other.timestamp {
             Ordering::Equal