git_ui: Commit modal refinement (#25484)

Closes #ISSUE

Release Notes:

- N/A *or* Added/Fixed/Improved ...

---------

Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>

crates/git_ui/src/git_panel.rs

@@ -184,6 +184,7 @@ pub struct GitPanel {
     pending_remote_operations: RemoteOperations,
     pub(crate) active_repository: Option<Entity<Repository>>,
     commit_editor: Entity<Editor>,
+    suggested_commit_message: Option<String>,
     conflicted_count: usize,
     conflicted_staged_count: usize,
     current_modifiers: Modifiers,
@@ -308,6 +309,7 @@ impl GitPanel {
                 remote_operation_id: 0,
                 active_repository,
                 commit_editor,
+                suggested_commit_message: None,
                 conflicted_count: 0,
                 conflicted_staged_count: 0,
                 current_modifiers: window.modifiers(),
@@ -1038,6 +1040,10 @@ impl GitPanel {
         .detach();
     }
 
+    pub fn total_staged_count(&self) -> usize {
+        self.tracked_staged_count + self.new_staged_count + self.conflicted_staged_count
+    }
+
     pub fn commit_message_buffer(&self, cx: &App) -> Entity<Buffer> {
         self.commit_editor
             .read(cx)
@@ -1200,6 +1206,57 @@ impl GitPanel {
         self.pending_commit = Some(task);
     }
 
+    /// Suggests a commit message based on the changed files and their statuses
+    pub fn suggest_commit_message(&self) -> Option<String> {
+        let entries = self
+            .entries
+            .iter()
+            .filter_map(|entry| {
+                if let GitListEntry::GitStatusEntry(status_entry) = entry {
+                    Some(status_entry)
+                } else {
+                    None
+                }
+            })
+            .collect::<Vec<&GitStatusEntry>>();
+
+        if entries.is_empty() {
+            None
+        } else if entries.len() == 1 {
+            let entry = &entries[0];
+            let file_name = entry
+                .repo_path
+                .file_name()
+                .unwrap_or_default()
+                .to_string_lossy();
+
+            if entry.status.is_deleted() {
+                Some(format!("Delete {}", file_name))
+            } else if entry.status.is_created() {
+                Some(format!("Create {}", file_name))
+            } else if entry.status.is_modified() {
+                Some(format!("Update {}", file_name))
+            } else {
+                None
+            }
+        } else {
+            None
+        }
+    }
+
+    fn update_editor_placeholder(&mut self, cx: &mut Context<Self>) {
+        let suggested_commit_message = self.suggest_commit_message();
+        self.suggested_commit_message = suggested_commit_message.clone();
+
+        if let Some(suggested_commit_message) = suggested_commit_message {
+            self.commit_editor.update(cx, |editor, cx| {
+                editor.set_placeholder_text(Arc::from(suggested_commit_message), cx)
+            });
+        }
+
+        cx.notify();
+    }
+
     fn fetch(&mut self, _: &git::Fetch, _window: &mut Window, cx: &mut Context<Self>) {
         let Some(repo) = self.active_repository.clone() else {
             return;
@@ -1444,6 +1501,7 @@ impl GitPanel {
                             git_panel.clear_pending();
                         }
                         git_panel.update_visible_entries(cx);
+                        git_panel.update_editor_placeholder(cx);
                     })
                     .ok();
             }