fix(ui): keep what is loaded on screen while it reloads

crates/ui/src/repository/model.rs

@@ -32,6 +32,12 @@ impl<T> LoadState<T> {
         matches!(self, Self::Loading)
     }
 
+    pub fn start_reload(&mut self) {
+        if self.ready().is_none() {
+            *self = Self::Loading;
+        }
+    }
+
     pub fn error(&self) -> Option<&str> {
         match self {
             Self::Failed(message) => Some(message),
@@ -297,6 +303,34 @@ mod tests {
         assert_eq!(index.tags.len(), 1);
     }
 
+    #[test]
+    fn a_reload_keeps_a_value_that_is_already_loaded() {
+        let mut state: LoadState<u8> = LoadState::Ready(1);
+        state.start_reload();
+        assert_eq!(state, LoadState::Ready(1));
+    }
+
+    #[test]
+    fn a_first_load_has_nothing_to_keep() {
+        let mut state: LoadState<u8> = LoadState::Idle;
+        state.start_reload();
+        assert_eq!(state, LoadState::Loading);
+    }
+
+    #[test]
+    fn a_reload_after_a_failure_has_nothing_to_keep() {
+        let mut state: LoadState<u8> = LoadState::Failed("boom".into());
+        state.start_reload();
+        assert_eq!(state, LoadState::Loading);
+    }
+
+    #[test]
+    fn a_reload_that_overtakes_another_stays_loading() {
+        let mut state: LoadState<u8> = LoadState::Loading;
+        state.start_reload();
+        assert_eq!(state, LoadState::Loading);
+    }
+
     #[test]
     fn load_state_exposes_only_the_matching_accessor() {
         let ready: LoadState<u8> = LoadState::Ready(1);

crates/ui/src/repository/state.rs

@@ -159,7 +159,7 @@ impl RepositoryState {
     /// immediately (`gpui::Task` semantics) — a later call always wins over an earlier one
     /// that has not yet applied its result.
     fn reload_head(&mut self, cx: &mut Context<Self>) {
-        self.head = LoadState::Loading;
+        self.head.start_reload();
         cx.notify();
         let path = self.path.clone();
         self.head_task = Some(cx.spawn(async move |this, cx| {
@@ -172,7 +172,7 @@ impl RepositoryState {
     }
 
     fn reload_references(&mut self, cx: &mut Context<Self>) {
-        self.references = LoadState::Loading;
+        self.references.start_reload();
         cx.notify();
         let path = self.path.clone();
         self.references_task = Some(cx.spawn(async move |this, cx| {
@@ -187,7 +187,7 @@ impl RepositoryState {
     /// The graph layout is computed in the same background closure as the walk that
     /// produces the commits it lays out, never after the result reaches the foreground.
     fn reload_history(&mut self, cx: &mut Context<Self>) {
-        self.history = LoadState::Loading;
+        self.history.start_reload();
         cx.notify();
         let path = self.path.clone();
         let scope = self.filter.scope.clone();