Git uncommit warning (#25977)

Adds a prompt when clicking the uncommit button when the current commit
is already present on a remote branch:

![screenshot showing
prompt](https://github.com/user-attachments/assets/d6421875-588e-4db0-aee0-a92f36bce94b)

Release Notes:

- N/A

---------

Co-authored-by: Conrad <conrad@zed.dev>

crates/git_ui/src/git_panel.rs

@@ -1265,34 +1265,20 @@ impl GitPanel {
             return;
         };
 
-        // TODO: Use git merge-base to find the upstream and main branch split
-        let confirmation = Task::ready(true);
-        // let confirmation = if self.commit_editor.read(cx).is_empty(cx) {
-        //     Task::ready(true)
-        // } else {
-        //     let prompt = window.prompt(
-        //         PromptLevel::Warning,
-        //         "Uncomitting will replace the current commit message with the previous commit's message",
-        //         None,
-        //         &["Ok", "Cancel"],
-        //         cx,
-        //     );
-        //     cx.spawn(|_, _| async move { prompt.await.is_ok_and(|i| i == 0) })
-        // };
-
+        let confirmation = self.check_for_pushed_commits(window, cx);
         let prior_head = self.load_commit_details("HEAD", cx);
 
         let task = cx.spawn_in(window, |this, mut cx| async move {
             let result = maybe!(async {
-                if !confirmation.await {
-                    Ok(None)
-                } else {
+                if let Ok(true) = confirmation.await {
                     let prior_head = prior_head.await?;
 
                     repo.update(&mut cx, |repo, _| repo.reset("HEAD^", ResetMode::Soft))?
                         .await??;
 
                     Ok(Some(prior_head))
+                } else {
+                    Ok(None)
                 }
             })
             .await;
@@ -1315,6 +1301,48 @@ impl GitPanel {
         self.pending_commit = Some(task);
     }
 
+    fn check_for_pushed_commits(
+        &mut self,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) -> impl Future<Output = Result<bool, anyhow::Error>> {
+        let repo = self.active_repository.clone();
+        let mut cx = window.to_async(cx);
+
+        async move {
+            let Some(repo) = repo else {
+                return Err(anyhow::anyhow!("No active repository"));
+            };
+
+            let pushed_to: Vec<SharedString> = repo
+                .update(&mut cx, |repo, _| repo.check_for_pushed_commits())?
+                .await??;
+
+            if pushed_to.is_empty() {
+                Ok(true)
+            } else {
+                #[derive(strum::EnumIter, strum::VariantNames)]
+                #[strum(serialize_all = "title_case")]
+                enum CancelUncommit {
+                    Uncommit,
+                    Cancel,
+                }
+                let detail = format!(
+                    "This commit was already pushed to {}.",
+                    pushed_to.into_iter().join(", ")
+                );
+                let result = cx
+                    .update(|window, cx| prompt("Are you sure?", Some(&detail), window, cx))?
+                    .await?;
+
+                match result {
+                    CancelUncommit::Cancel => Ok(false),
+                    CancelUncommit::Uncommit => Ok(true),
+                }
+            }
+        }
+    }
+
     /// Suggests a commit message based on the changed files and their statuses
     pub fn suggest_commit_message(&self) -> Option<String> {
         if self.total_staged_count() != 1 {