view: remove git heads from view when forgetting workspace (but not w…

…hen merging view, yet)

cli/src/commands/workspace/forget.rs

@@ -89,8 +89,11 @@ pub fn cmd_workspace_forget(
     // bundle every workspace forget into a single transaction, so that e.g.
     // undo correctly restores all of them at once.
     let mut tx = workspace_command.start_transaction();
-    wss.iter()
-        .try_for_each(|ws| tx.repo_mut().remove_wc_commit(ws))?;
+    wss.iter().try_for_each(|ws| {
+        tx.repo_mut().remove_git_head_target(ws);
+        tx.repo_mut().remove_wc_commit(ws)
+    })?;
+
     let description = if let [ws] = wss.as_slice() {
         format!("forget workspace {}", ws.as_str())
     } else {

lib/src/repo.rs

@@ -1346,6 +1346,10 @@ impl MutableRepo {
         Ok(())
     }
 
+    pub fn remove_git_head_target(&mut self, workspace_id: &WorkspaceId) {
+        self.view_mut().remove_git_head_target(workspace_id);
+    }
+
     pub fn remove_wc_commit(&mut self, workspace_id: &WorkspaceId) -> Result<(), EditCommitError> {
         self.maybe_abandon_wc_commit(workspace_id)?;
         self.view_mut().remove_wc_commit(workspace_id);
@@ -1656,6 +1660,9 @@ impl MutableRepo {
             } else {
                 // The other side removed the workspace. We want to remove it even if the self
                 // side changed the working-copy commit.
+                // TODO: remove the git_heads entry as well. May want to migrate to a
+                // HashMap<WorkspaceId, WorkspaceView> in the View, and simply remove a workspace
+                // all at once. However this proved more tricky than expected.
                 self.view_mut().remove_wc_commit(workspace_id);
             }
         }

lib/src/view.rs

@@ -324,6 +324,10 @@ impl View {
         self.data.git_heads = git_heads;
     }
 
+    pub(crate) fn remove_git_head_target(&mut self, workspace_id: &WorkspaceId) {
+        self.data.git_heads.remove(workspace_id);
+    }
+
     /// Iterates all commit ids referenced by this view.
     ///
     /// This can include hidden commits referenced by remote branches, previous