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/src/repository.rs

@@ -202,8 +202,12 @@ pub trait GitRepository: Send + Sync {
         options: Option<PushOptions>,
     ) -> Result<RemoteCommandOutput>;
     fn pull(&self, branch_name: &str, upstream_name: &str) -> Result<RemoteCommandOutput>;
-    fn get_remotes(&self, branch_name: Option<&str>) -> Result<Vec<Remote>>;
     fn fetch(&self) -> Result<RemoteCommandOutput>;
+
+    fn get_remotes(&self, branch_name: Option<&str>) -> Result<Vec<Remote>>;
+
+    /// returns a list of remote branches that contain HEAD
+    fn check_for_pushed_commit(&self) -> Result<Vec<SharedString>>;
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Deserialize, JsonSchema)]
@@ -781,6 +785,54 @@ impl GitRepository for RealGitRepository {
             ));
         }
     }
+
+    fn check_for_pushed_commit(&self) -> Result<Vec<SharedString>> {
+        let working_directory = self.working_directory()?;
+        let git_cmd = |args: &[&str]| -> Result<String> {
+            let output = new_std_command(&self.git_binary_path)
+                .current_dir(&working_directory)
+                .args(args)
+                .output()?;
+            if output.status.success() {
+                Ok(String::from_utf8(output.stdout)?)
+            } else {
+                Err(anyhow!(String::from_utf8_lossy(&output.stderr).to_string()))
+            }
+        };
+
+        let head = git_cmd(&["rev-parse", "HEAD"])
+            .context("Failed to get HEAD")?
+            .trim()
+            .to_owned();
+
+        let mut remote_branches = vec![];
+        let mut add_if_matching = |remote_head: &str| {
+            if let Ok(merge_base) = git_cmd(&["merge-base", &head, remote_head]) {
+                if merge_base.trim() == head {
+                    if let Some(s) = remote_head.strip_prefix("refs/remotes/") {
+                        remote_branches.push(s.to_owned().into());
+                    }
+                }
+            }
+        };
+
+        // check the main branch of each remote
+        let remotes = git_cmd(&["remote"]).context("Failed to get remotes")?;
+        for remote in remotes.lines() {
+            if let Ok(remote_head) =
+                git_cmd(&["symbolic-ref", &format!("refs/remotes/{remote}/HEAD")])
+            {
+                add_if_matching(remote_head.trim());
+            }
+        }
+
+        // ... and the remote branch that the checked-out one is tracking
+        if let Ok(remote_head) = git_cmd(&["rev-parse", "--symbolic-full-name", "@{u}"]) {
+            add_if_matching(remote_head.trim());
+        }
+
+        Ok(remote_branches)
+    }
 }
 
 #[cfg(not(windows))]
@@ -998,6 +1050,10 @@ impl GitRepository for FakeGitRepository {
     fn get_remotes(&self, _branch: Option<&str>) -> Result<Vec<Remote>> {
         unimplemented!()
     }
+
+    fn check_for_pushed_commit(&self) -> Result<Vec<SharedString>> {
+        unimplemented!()
+    }
 }
 
 fn check_path_to_repo_path_errors(relative_file_path: &Path) -> Result<()> {