git: Add option to branch from default branch in branch picker (#34663)

Closes #33700

The option shows up as an icon that appears on entries that would create
a new branch. You can also branch from the default by secondary
confirming, which the icon has a tooltip for as well.

We based the default branch on the results from this command: `git
symbolic-ref refs/remotes/upstream/HEAD` and fallback to `git
symbolic-ref refs/remotes/origin/HEAD`

Release Notes:

- Add option to create a branch from a default branch in git branch
picker

---------

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

crates/git_ui/src/branch_picker.rs

@@ -13,7 +13,7 @@ use project::git_store::Repository;
 use std::sync::Arc;
 use time::OffsetDateTime;
 use time_format::format_local_timestamp;
-use ui::{HighlightedLabel, ListItem, ListItemSpacing, prelude::*};
+use ui::{HighlightedLabel, ListItem, ListItemSpacing, Tooltip, prelude::*};
 use util::ResultExt;
 use workspace::notifications::DetachAndPromptErr;
 use workspace::{ModalView, Workspace};
@@ -90,11 +90,21 @@ impl BranchList {
         let all_branches_request = repository
             .clone()
             .map(|repository| repository.update(cx, |repository, _| repository.branches()));
+        let default_branch_request = repository
+            .clone()
+            .map(|repository| repository.update(cx, |repository, _| repository.default_branch()));
 
         cx.spawn_in(window, async move |this, cx| {
             let mut all_branches = all_branches_request
                 .context("No active repository")?
                 .await??;
+            let default_branch = default_branch_request
+                .context("No active repository")?
+                .await
+                .map(Result::ok)
+                .ok()
+                .flatten()
+                .flatten();
 
             let all_branches = cx
                 .background_spawn(async move {
@@ -124,6 +134,7 @@ impl BranchList {
 
             this.update_in(cx, |this, window, cx| {
                 this.picker.update(cx, |picker, cx| {
+                    picker.delegate.default_branch = default_branch;
                     picker.delegate.all_branches = Some(all_branches);
                     picker.refresh(window, cx);
                 })
@@ -192,6 +203,7 @@ struct BranchEntry {
 pub struct BranchListDelegate {
     matches: Vec<BranchEntry>,
     all_branches: Option<Vec<Branch>>,
+    default_branch: Option<SharedString>,
     repo: Option<Entity<Repository>>,
     style: BranchListStyle,
     selected_index: usize,
@@ -206,6 +218,7 @@ impl BranchListDelegate {
             repo,
             style,
             all_branches: None,
+            default_branch: None,
             selected_index: 0,
             last_query: Default::default(),
             modifiers: Default::default(),
@@ -214,6 +227,7 @@ impl BranchListDelegate {
 
     fn create_branch(
         &self,
+        from_branch: Option<SharedString>,
         new_branch_name: SharedString,
         window: &mut Window,
         cx: &mut Context<Picker<Self>>,
@@ -223,6 +237,11 @@ impl BranchListDelegate {
         };
         let new_branch_name = new_branch_name.to_string().replace(' ', "-");
         cx.spawn(async move |_, cx| {
+            if let Some(based_branch) = from_branch {
+                repo.update(cx, |repo, _| repo.change_branch(based_branch.to_string()))?
+                    .await??;
+            }
+
             repo.update(cx, |repo, _| {
                 repo.create_branch(new_branch_name.to_string())
             })?
@@ -353,12 +372,22 @@ impl PickerDelegate for BranchListDelegate {
         })
     }
 
-    fn confirm(&mut self, _secondary: bool, window: &mut Window, cx: &mut Context<Picker<Self>>) {
+    fn confirm(&mut self, secondary: bool, window: &mut Window, cx: &mut Context<Picker<Self>>) {
         let Some(entry) = self.matches.get(self.selected_index()) else {
             return;
         };
         if entry.is_new {
-            self.create_branch(entry.branch.name().to_owned().into(), window, cx);
+            let from_branch = if secondary {
+                self.default_branch.clone()
+            } else {
+                None
+            };
+            self.create_branch(
+                from_branch,
+                entry.branch.name().to_owned().into(),
+                window,
+                cx,
+            );
             return;
         }
 
@@ -439,6 +468,28 @@ impl PickerDelegate for BranchListDelegate {
             })
             .unwrap_or_else(|| (None, None));
 
+        let icon = if let Some(default_branch) = self.default_branch.clone()
+            && entry.is_new
+        {
+            Some(
+                IconButton::new("branch-from-default", IconName::GitBranchSmall)
+                    .on_click(cx.listener(move |this, _, window, cx| {
+                        this.delegate.set_selected_index(ix, window, cx);
+                        this.delegate.confirm(true, window, cx);
+                    }))
+                    .tooltip(move |window, cx| {
+                        Tooltip::for_action(
+                            format!("Create branch based off default: {default_branch}"),
+                            &menu::SecondaryConfirm,
+                            window,
+                            cx,
+                        )
+                    }),
+            )
+        } else {
+            None
+        };
+
         let branch_name = if entry.is_new {
             h_flex()
                 .gap_1()
@@ -504,7 +555,8 @@ impl PickerDelegate for BranchListDelegate {
                                     .color(Color::Muted)
                             }))
                         }),
-                ),
+                )
+                .end_slot::<IconButton>(icon),
         )
     }