Make repo and branch popovers extend up from their trigger buttons (#26950)

Previously, when clicking on the branch, the popover would obscure the
button you just clicked, which was awkward.

Release Notes:

- Improved the placement of the repo and branch picker popovers in the
git panel.
- Added a 'SelectRepo' action that opens the repository selector in a
modal.

crates/git_ui/src/branch_picker.rs

@@ -7,7 +7,7 @@ use gpui::{
     InteractiveElement, IntoElement, Modifiers, ModifiersChangedEvent, ParentElement, Render,
     SharedString, Styled, Subscription, Task, Window,
 };
-use picker::{Picker, PickerDelegate};
+use picker::{Picker, PickerDelegate, PickerEditorPosition};
 use project::git::Repository;
 use std::sync::Arc;
 use time::OffsetDateTime;
@@ -17,13 +17,10 @@ use util::ResultExt;
 use workspace::notifications::DetachAndPromptErr;
 use workspace::{ModalView, Workspace};
 
-pub fn init(cx: &mut App) {
-    cx.observe_new(|workspace: &mut Workspace, _, _| {
-        workspace.register_action(open);
-        workspace.register_action(switch);
-        workspace.register_action(checkout_branch);
-    })
-    .detach();
+pub fn register(workspace: &mut Workspace) {
+    workspace.register_action(open);
+    workspace.register_action(switch);
+    workspace.register_action(checkout_branch);
 }
 
 pub fn checkout_branch(
@@ -225,6 +222,13 @@ impl PickerDelegate for BranchListDelegate {
         "Select branch...".into()
     }
 
+    fn editor_position(&self) -> PickerEditorPosition {
+        match self.style {
+            BranchListStyle::Modal => PickerEditorPosition::Start,
+            BranchListStyle::Popover => PickerEditorPosition::End,
+        }
+    }
+
     fn match_count(&self) -> usize {
         self.matches.len()
     }