git_ui: Add setting to control default click behavior for git panel (#59649)

# Objective

The current behavior of the git panel is that when you click a file it
will open the multi-buffer view that shows all files with changes. If
you use CMD+Click or CTRL+Click, it will open the solo-file experience
where you only see the diff of the file you have selected. But, there is
no way to customize this behavior.

Related to:
https://github.com/zed-industries/zed/pull/56152#issuecomment-4641971669

## Solution

This MR adds a setting that allows you to customize the default click
behavior. The alternate behavior will always be accessible via CMD+Click
or CTRL+Click.

## Self-Review Checklist:

- [X] I've reviewed my own diff for quality, security, and reliability
- [X] Unsafe blocks (if any) have justifying comments
- [X] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [X] Tests cover the new/changed behavior
- [X] Performance impact has been considered and is acceptable

---

Release Notes:

- Added a setting to control default click behavior for git panel files

---------

Co-authored-by: Christopher Biscardi <chris@christopherbiscardi.com>

assets/settings/default.json

@@ -1014,6 +1014,11 @@
     //
     // Default: 0
     "commit_title_max_length": 0,
+    // Default action when clicking a changed file in the Git panel.
+    //
+    // Choices: project_diff, file_diff, view_file
+    // Default: project_diff
+    "entry_primary_click_action": "project_diff",
   },
   "message_editor": {
     // Whether to automatically replace emoji shortcodes with emoji characters.

crates/git_ui/src/git_panel.rs

@@ -63,7 +63,8 @@ use prompt_store::RULES_FILE_NAMES;
 use proto::RpcError;
 use serde::{Deserialize, Serialize};
 use settings::{
-    GitPanelGroupBy, GitPanelSortBy, Settings, SettingsStore, StatusStyle, update_settings_file,
+    GitPanelClickBehavior, GitPanelGroupBy, GitPanelSortBy, Settings, SettingsStore, StatusStyle,
+    update_settings_file,
 };
 use smallvec::SmallVec;
 use std::future::Future;
@@ -1489,6 +1490,36 @@ impl GitPanel {
         });
     }
 
+    fn open_selected_entry_on_click(
+        &mut self,
+        secondary: bool,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) {
+        let entry_primary_click_action =
+            GitPanelSettings::get_global(cx).entry_primary_click_action;
+        let action = match (entry_primary_click_action, secondary) {
+            (GitPanelClickBehavior::ProjectDiff, false) => GitPanelClickBehavior::ProjectDiff,
+            (GitPanelClickBehavior::ProjectDiff, true) => GitPanelClickBehavior::FileDiff,
+            (GitPanelClickBehavior::FileDiff, false) => GitPanelClickBehavior::FileDiff,
+            (GitPanelClickBehavior::FileDiff, true) => GitPanelClickBehavior::ProjectDiff,
+            (GitPanelClickBehavior::ViewFile, false) => GitPanelClickBehavior::ViewFile,
+            (GitPanelClickBehavior::ViewFile, true) => GitPanelClickBehavior::ProjectDiff,
+        };
+        match action {
+            GitPanelClickBehavior::ProjectDiff => {
+                self.open_diff(&Default::default(), window, cx);
+                self.focus_handle.focus(window, cx);
+            }
+            GitPanelClickBehavior::FileDiff => {
+                self.open_solo_diff(&Default::default(), window, cx);
+            }
+            GitPanelClickBehavior::ViewFile => {
+                self.view_file(&Default::default(), window, cx);
+            }
+        }
+    }
+
     fn revert_selected(
         &mut self,
         action: &git::RestoreFile,
@@ -6493,12 +6524,7 @@ impl GitPanel {
                 cx.listener(move |this, event: &ClickEvent, window, cx| {
                     this.selected_entry = Some(ix);
                     cx.notify();
-                    if event.modifiers().secondary() {
-                        this.open_solo_diff(&Default::default(), window, cx)
-                    } else {
-                        this.open_diff(&Default::default(), window, cx);
-                        this.focus_handle.focus(window, cx);
-                    }
+                    this.open_selected_entry_on_click(event.modifiers().secondary(), window, cx);
                 })
             })
             .on_mouse_down(

crates/git_ui/src/git_panel_settings.rs

@@ -2,7 +2,9 @@ use editor::{EditorSettings, ui_scrollbar_settings_from_raw};
 use gpui::Pixels;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
-use settings::{GitPanelGroupBy, GitPanelSortBy, RegisterSetting, Settings, StatusStyle};
+use settings::{
+    GitPanelClickBehavior, GitPanelGroupBy, GitPanelSortBy, RegisterSetting, Settings, StatusStyle,
+};
 use ui::{
     px,
     scrollbars::{ScrollbarVisibility, ShowScrollbar},
@@ -32,6 +34,7 @@ pub struct GitPanelSettings {
     pub show_count_badge: bool,
     pub starts_open: bool,
     pub commit_title_max_length: usize,
+    pub entry_primary_click_action: GitPanelClickBehavior,
 }
 
 #[derive(Default)]
@@ -80,6 +83,7 @@ impl Settings for GitPanelSettings {
             show_count_badge: git_panel.show_count_badge.unwrap(),
             starts_open: git_panel.starts_open.unwrap(),
             commit_title_max_length: git_panel.commit_title_max_length.unwrap(),
+            entry_primary_click_action: git_panel.entry_primary_click_action.unwrap(),
         }
     }
 }

crates/settings_content/src/settings_content.rs

@@ -718,6 +718,36 @@ pub struct GitPanelSettingsContent {
     ///
     /// Default: 0
     pub commit_title_max_length: Option<usize>,
+
+    /// Default action when clicking a changed file in the Git panel.
+    ///
+    /// Default: project_diff
+    pub entry_primary_click_action: Option<GitPanelClickBehavior>,
+}
+
+#[derive(
+    Default,
+    Copy,
+    Clone,
+    Debug,
+    Serialize,
+    Deserialize,
+    JsonSchema,
+    MergeFrom,
+    PartialEq,
+    Eq,
+    strum::VariantArray,
+    strum::VariantNames,
+)]
+#[serde(rename_all = "snake_case")]
+pub enum GitPanelClickBehavior {
+    /// Open the project diff, showing all changed files.
+    #[default]
+    ProjectDiff,
+    /// Open a single-file diff view.
+    FileDiff,
+    /// Open the file in the editor without a diff view.
+    ViewFile,
 }
 
 #[derive(

crates/settings_ui/src/page_data.rs

@@ -5776,7 +5776,7 @@ fn panels_page() -> SettingsPage {
         ]
     }
 
-    fn git_panel_section() -> [SettingsPageItem; 16] {
+    fn git_panel_section() -> [SettingsPageItem; 17] {
         [
             SettingsPageItem::SectionHeader("Git Panel"),
             SettingsPageItem::SettingItem(SettingItem {
@@ -5992,6 +5992,29 @@ fn panels_page() -> SettingsPage {
                 metadata: None,
                 files: USER,
             }),
+            SettingsPageItem::SettingItem(SettingItem {
+                title: "Primary Click Behavior",
+                description: "Default action when clicking a changed file in the Git panel.",
+                field: Box::new(SettingField {
+                    organization_override: None,
+                    json_path: Some("git_panel.entry_primary_click_action"),
+                    pick: |settings_content| {
+                        settings_content
+                            .git_panel
+                            .as_ref()?
+                            .entry_primary_click_action
+                            .as_ref()
+                    },
+                    write: |settings_content, value, _| {
+                        settings_content
+                            .git_panel
+                            .get_or_insert_default()
+                            .entry_primary_click_action = value;
+                    },
+                }),
+                metadata: None,
+                files: USER,
+            }),
             SettingsPageItem::SettingItem(SettingItem {
                 title: "Show Count Badge",
                 description: "Whether to show a badge on the git panel icon with the count of uncommitted changes.",

crates/settings_ui/src/settings_ui.rs

@@ -600,6 +600,7 @@ fn init_renderers(cx: &mut App) {
         .add_basic_renderer::<settings::ThinkingBlockDisplay>(render_dropdown)
         .add_basic_renderer::<settings::ImageFileSizeUnit>(render_dropdown)
         .add_basic_renderer::<settings::StatusStyle>(render_dropdown)
+        .add_basic_renderer::<settings::GitPanelClickBehavior>(render_dropdown)
         .add_basic_renderer::<settings::GitPanelSortBy>(render_dropdown)
         .add_basic_renderer::<settings::GitPanelGroupBy>(render_dropdown)
         .add_basic_renderer::<settings::EncodingDisplayOptions>(render_dropdown)