Add staged variants of the hunk_style controls (#26259)

This PR adds a few more hunk style settings that flips the emphasis.
Normally, the concept at Zed has been that the project diff should
emphasize what's going into the commit. However, this leads to a problem
where the default state of all diff hunks are in the non-emphasized
state, making them hard to see and interact with. Especially on light
themes. This PR is an experiment in flipping the emphasis states. Now
the project diff is more like a queue of work, with the next "job" (hunk
to be evaluated) emphasized, and the "completed" (staged) hunks
deemphasized. This fixes the default state issue but is a big jump from
how we've been thinking about it. So here we can try it out and see how
it feels :)

Release Notes:

- Git Beta: Added hunk style settings to emphasize the unstaged state,
rather than the staged state.

crates/editor/src/element.rs

@@ -4349,6 +4349,11 @@ impl EditorElement {
     fn paint_gutter_diff_hunks(layout: &mut EditorLayout, window: &mut Window, cx: &mut App) {
         let is_light = cx.theme().appearance().is_light();
 
+        let hunk_style = ProjectSettings::get_global(cx)
+            .git
+            .hunk_style
+            .unwrap_or_default();
+
         if layout.display_hunks.is_empty() {
             return;
         }
@@ -4412,9 +4417,20 @@ impl EditorElement {
                 if let Some((hunk_bounds, mut background_color, corner_radii, secondary_status)) =
                     hunk_to_paint
                 {
-                    if secondary_status.has_secondary_hunk() {
-                        background_color =
-                            background_color.opacity(if is_light { 0.2 } else { 0.32 });
+                    match hunk_style {
+                        GitHunkStyleSetting::Transparent | GitHunkStyleSetting::Pattern => {
+                            if secondary_status.has_secondary_hunk() {
+                                background_color =
+                                    background_color.opacity(if is_light { 0.2 } else { 0.32 });
+                            }
+                        }
+                        GitHunkStyleSetting::StagedPattern
+                        | GitHunkStyleSetting::StagedTransparent => {
+                            if !secondary_status.has_secondary_hunk() {
+                                background_color =
+                                    background_color.opacity(if is_light { 0.2 } else { 0.32 });
+                            }
+                        }
                     }
 
                     // Flatten the background color with the editor color to prevent
@@ -6734,10 +6750,10 @@ impl Element for EditorElement {
                         .update(cx, |editor, cx| editor.highlighted_display_rows(window, cx));
 
                     let is_light = cx.theme().appearance().is_light();
-                    let use_pattern = ProjectSettings::get_global(cx)
+                    let hunk_style = ProjectSettings::get_global(cx)
                         .git
                         .hunk_style
-                        .map_or(false, |style| matches!(style, GitHunkStyleSetting::Pattern));
+                        .unwrap_or_default();
 
                     for (ix, row_info) in row_infos.iter().enumerate() {
                         let Some(diff_status) = row_info.diff_status else {
@@ -6757,20 +6773,39 @@ impl Element for EditorElement {
 
                         let unstaged = diff_status.has_secondary_hunk();
                         let hunk_opacity = if is_light { 0.16 } else { 0.12 };
+                        let slash_width = line_height.0 / 1.5; // ~16 by default
 
-                        let staged_background =
-                            solid_background(background_color.opacity(hunk_opacity));
-                        let unstaged_background = if use_pattern {
-                            pattern_slash(
-                                background_color.opacity(hunk_opacity),
-                                window.rem_size().0 * 1.125, // ~18 by default
-                            )
-                        } else {
-                            solid_background(background_color.opacity(if is_light {
-                                0.08
-                            } else {
-                                0.04
-                            }))
+                        let staged_background = match hunk_style {
+                            GitHunkStyleSetting::Transparent | GitHunkStyleSetting::Pattern => {
+                                solid_background(background_color.opacity(hunk_opacity))
+                            }
+                            GitHunkStyleSetting::StagedPattern => {
+                                pattern_slash(background_color.opacity(hunk_opacity), slash_width)
+                            }
+                            GitHunkStyleSetting::StagedTransparent => {
+                                solid_background(background_color.opacity(if is_light {
+                                    0.08
+                                } else {
+                                    0.04
+                                }))
+                            }
+                        };
+
+                        let unstaged_background = match hunk_style {
+                            GitHunkStyleSetting::Transparent => {
+                                solid_background(background_color.opacity(if is_light {
+                                    0.08
+                                } else {
+                                    0.04
+                                }))
+                            }
+                            GitHunkStyleSetting::Pattern => {
+                                pattern_slash(background_color.opacity(hunk_opacity), slash_width)
+                            }
+                            GitHunkStyleSetting::StagedPattern
+                            | GitHunkStyleSetting::StagedTransparent => {
+                                solid_background(background_color.opacity(hunk_opacity))
+                            }
                         };
 
                         let background = if unstaged {

crates/project/src/project_settings.rs

@@ -212,6 +212,10 @@ pub enum GitHunkStyleSetting {
     Transparent,
     /// Show unstaged hunks with a pattern background
     Pattern,
+    /// Show staged hunks with a pattern background
+    StagedPattern,
+    /// Show staged hunks with a pattern background
+    StagedTransparent,
 }
 
 #[derive(Clone, Copy, Debug, Default, Serialize, Deserialize, JsonSchema)]