Diff command (#2476)

codex-rs/core/src/git_info.rs

@@ -1,11 +1,16 @@
+use std::collections::HashSet;
 use std::path::Path;
 
+use codex_protocol::mcp_protocol::GitSha;
+use futures::future::join_all;
 use serde::Deserialize;
 use serde::Serialize;
 use tokio::process::Command;
 use tokio::time::Duration as TokioDuration;
 use tokio::time::timeout;
 
+use crate::util::is_inside_git_repo;
+
 /// Timeout for git commands to prevent freezing on large repositories
 const GIT_COMMAND_TIMEOUT: TokioDuration = TokioDuration::from_secs(5);
 
@@ -22,6 +27,12 @@ pub struct GitInfo {
     pub repository_url: Option<String>,
 }
 
+#[derive(Serialize, Deserialize, Clone, Debug)]
+pub struct GitDiffToRemote {
+    pub sha: GitSha,
+    pub diff: String,
+}
+
 /// Collect git repository information from the given working directory using command-line git.
 /// Returns None if no git repository is found or if git operations fail.
 /// Uses timeouts to prevent freezing on large repositories.
@@ -80,6 +91,23 @@ pub async fn collect_git_info(cwd: &Path) -> Option<GitInfo> {
     Some(git_info)
 }
 
+/// Returns the closest git sha to HEAD that is on a remote as well as the diff to that sha.
+pub async fn git_diff_to_remote(cwd: &Path) -> Option<GitDiffToRemote> {
+    if !is_inside_git_repo(cwd) {
+        return None;
+    }
+
+    let remotes = get_git_remotes(cwd).await?;
+    let branches = branch_ancestry(cwd).await?;
+    let base_sha = find_closest_sha(cwd, &branches, &remotes).await?;
+    let diff = diff_against_sha(cwd, &base_sha).await?;
+
+    Some(GitDiffToRemote {
+        sha: base_sha,
+        diff,
+    })
+}
+
 /// Run a git command with a timeout to prevent blocking on large repositories
 async fn run_git_command_with_timeout(args: &[&str], cwd: &Path) -> Option<std::process::Output> {
     let result = timeout(
@@ -94,6 +122,309 @@ async fn run_git_command_with_timeout(args: &[&str], cwd: &Path) -> Option<std::
     }
 }
 
+async fn get_git_remotes(cwd: &Path) -> Option<Vec<String>> {
+    let output = run_git_command_with_timeout(&["remote"], cwd).await?;
+    if !output.status.success() {
+        return None;
+    }
+    let mut remotes: Vec<String> = String::from_utf8(output.stdout)
+        .ok()?
+        .lines()
+        .map(|s| s.to_string())
+        .collect();
+    if let Some(pos) = remotes.iter().position(|r| r == "origin") {
+        let origin = remotes.remove(pos);
+        remotes.insert(0, origin);
+    }
+    Some(remotes)
+}
+
+/// Attempt to determine the repository's default branch name.
+///
+/// Preference order:
+/// 1) The symbolic ref at `refs/remotes/<remote>/HEAD` for the first remote (origin prioritized)
+/// 2) `git remote show <remote>` parsed for "HEAD branch: <name>"
+/// 3) Local fallback to existing `main` or `master` if present
+async fn get_default_branch(cwd: &Path) -> Option<String> {
+    // Prefer the first remote (with origin prioritized)
+    let remotes = get_git_remotes(cwd).await.unwrap_or_default();
+    for remote in remotes {
+        // Try symbolic-ref, which returns something like: refs/remotes/origin/main
+        if let Some(symref_output) = run_git_command_with_timeout(
+            &[
+                "symbolic-ref",
+                "--quiet",
+                &format!("refs/remotes/{remote}/HEAD"),
+            ],
+            cwd,
+        )
+        .await
+            && symref_output.status.success()
+            && let Ok(sym) = String::from_utf8(symref_output.stdout)
+        {
+            let trimmed = sym.trim();
+            if let Some((_, name)) = trimmed.rsplit_once('/') {
+                return Some(name.to_string());
+            }
+        }
+
+        // Fall back to parsing `git remote show <remote>` output
+        if let Some(show_output) =
+            run_git_command_with_timeout(&["remote", "show", &remote], cwd).await
+            && show_output.status.success()
+            && let Ok(text) = String::from_utf8(show_output.stdout)
+        {
+            for line in text.lines() {
+                let line = line.trim();
+                if let Some(rest) = line.strip_prefix("HEAD branch:") {
+                    let name = rest.trim();
+                    if !name.is_empty() {
+                        return Some(name.to_string());
+                    }
+                }
+            }
+        }
+    }
+
+    // No remote-derived default; try common local defaults if they exist
+    for candidate in ["main", "master"] {
+        if let Some(verify) = run_git_command_with_timeout(
+            &[
+                "rev-parse",
+                "--verify",
+                "--quiet",
+                &format!("refs/heads/{candidate}"),
+            ],
+            cwd,
+        )
+        .await
+            && verify.status.success()
+        {
+            return Some(candidate.to_string());
+        }
+    }
+
+    None
+}
+
+/// Build an ancestry of branches starting at the current branch and ending at the
+/// repository's default branch (if determinable)..
+async fn branch_ancestry(cwd: &Path) -> Option<Vec<String>> {
+    // Discover current branch (ignore detached HEAD by treating it as None)
+    let current_branch = run_git_command_with_timeout(&["rev-parse", "--abbrev-ref", "HEAD"], cwd)
+        .await
+        .and_then(|o| {
+            if o.status.success() {
+                String::from_utf8(o.stdout).ok()
+            } else {
+                None
+            }
+        })
+        .map(|s| s.trim().to_string())
+        .filter(|s| s != "HEAD");
+
+    // Discover default branch
+    let default_branch = get_default_branch(cwd).await;
+
+    let mut ancestry: Vec<String> = Vec::new();
+    let mut seen: HashSet<String> = HashSet::new();
+    if let Some(cb) = current_branch.clone() {
+        seen.insert(cb.clone());
+        ancestry.push(cb);
+    }
+    if let Some(db) = default_branch
+        && !seen.contains(&db)
+    {
+        seen.insert(db.clone());
+        ancestry.push(db);
+    }
+
+    // Expand candidates: include any remote branches that already contain HEAD.
+    // This addresses cases where we're on a new local-only branch forked from a
+    // remote branch that isn't the repository default. We prioritize remotes in
+    // the order returned by get_git_remotes (origin first).
+    let remotes = get_git_remotes(cwd).await.unwrap_or_default();
+    for remote in remotes {
+        if let Some(output) = run_git_command_with_timeout(
+            &[
+                "for-each-ref",
+                "--format=%(refname:short)",
+                "--contains=HEAD",
+                &format!("refs/remotes/{remote}"),
+            ],
+            cwd,
+        )
+        .await
+            && output.status.success()
+            && let Ok(text) = String::from_utf8(output.stdout)
+        {
+            for line in text.lines() {
+                let short = line.trim();
+                // Expect format like: "origin/feature"; extract the branch path after "remote/"
+                if let Some(stripped) = short.strip_prefix(&format!("{remote}/"))
+                    && !stripped.is_empty()
+                    && !seen.contains(stripped)
+                {
+                    seen.insert(stripped.to_string());
+                    ancestry.push(stripped.to_string());
+                }
+            }
+        }
+    }
+
+    // Ensure we return Some vector, even if empty, to allow caller logic to proceed
+    Some(ancestry)
+}
+
+// Helper for a single branch: return the remote SHA if present on any remote
+// and the distance (commits ahead of HEAD) for that branch. The first item is
+// None if the branch is not present on any remote. Returns None if distance
+// could not be computed due to git errors/timeouts.
+async fn branch_remote_and_distance(
+    cwd: &Path,
+    branch: &str,
+    remotes: &[String],
+) -> Option<(Option<GitSha>, usize)> {
+    // Try to find the first remote ref that exists for this branch (origin prioritized by caller).
+    let mut found_remote_sha: Option<GitSha> = None;
+    let mut found_remote_ref: Option<String> = None;
+    for remote in remotes {
+        let remote_ref = format!("refs/remotes/{remote}/{branch}");
+        let Some(verify_output) =
+            run_git_command_with_timeout(&["rev-parse", "--verify", "--quiet", &remote_ref], cwd)
+                .await
+        else {
+            // Mirror previous behavior: if the verify call times out/fails at the process level,
+            // treat the entire branch as unusable.
+            return None;
+        };
+        if !verify_output.status.success() {
+            continue;
+        }
+        let Ok(sha) = String::from_utf8(verify_output.stdout) else {
+            // Mirror previous behavior and skip the entire branch on parse failure.
+            return None;
+        };
+        found_remote_sha = Some(GitSha::new(sha.trim()));
+        found_remote_ref = Some(remote_ref);
+        break;
+    }
+
+    // Compute distance as the number of commits HEAD is ahead of the branch.
+    // Prefer local branch name if it exists; otherwise fall back to the remote ref (if any).
+    let count_output = if let Some(local_count) =
+        run_git_command_with_timeout(&["rev-list", "--count", &format!("{branch}..HEAD")], cwd)
+            .await
+    {
+        if local_count.status.success() {
+            local_count
+        } else if let Some(remote_ref) = &found_remote_ref {
+            match run_git_command_with_timeout(
+                &["rev-list", "--count", &format!("{remote_ref}..HEAD")],
+                cwd,
+            )
+            .await
+            {
+                Some(remote_count) => remote_count,
+                None => return None,
+            }
+        } else {
+            return None;
+        }
+    } else if let Some(remote_ref) = &found_remote_ref {
+        match run_git_command_with_timeout(
+            &["rev-list", "--count", &format!("{remote_ref}..HEAD")],
+            cwd,
+        )
+        .await
+        {
+            Some(remote_count) => remote_count,
+            None => return None,
+        }
+    } else {
+        return None;
+    };
+
+    if !count_output.status.success() {
+        return None;
+    }
+    let Ok(distance_str) = String::from_utf8(count_output.stdout) else {
+        return None;
+    };
+    let Ok(distance) = distance_str.trim().parse::<usize>() else {
+        return None;
+    };
+
+    Some((found_remote_sha, distance))
+}
+
+// Finds the closest sha that exist on any of branches and also exists on any of the remotes.
+async fn find_closest_sha(cwd: &Path, branches: &[String], remotes: &[String]) -> Option<GitSha> {
+    // A sha and how many commits away from HEAD it is.
+    let mut closest_sha: Option<(GitSha, usize)> = None;
+    for branch in branches {
+        let Some((maybe_remote_sha, distance)) =
+            branch_remote_and_distance(cwd, branch, remotes).await
+        else {
+            continue;
+        };
+        let Some(remote_sha) = maybe_remote_sha else {
+            // Preserve existing behavior: skip branches that are not present on a remote.
+            continue;
+        };
+        match &closest_sha {
+            None => closest_sha = Some((remote_sha, distance)),
+            Some((_, best_distance)) if distance < *best_distance => {
+                closest_sha = Some((remote_sha, distance));
+            }
+            _ => {}
+        }
+    }
+    closest_sha.map(|(sha, _)| sha)
+}
+
+async fn diff_against_sha(cwd: &Path, sha: &GitSha) -> Option<String> {
+    let output = run_git_command_with_timeout(&["diff", &sha.0], cwd).await?;
+    // 0 is success and no diff.
+    // 1 is success but there is a diff.
+    let exit_ok = output.status.code().is_some_and(|c| c == 0 || c == 1);
+    if !exit_ok {
+        return None;
+    }
+    let mut diff = String::from_utf8(output.stdout).ok()?;
+
+    if let Some(untracked_output) =
+        run_git_command_with_timeout(&["ls-files", "--others", "--exclude-standard"], cwd).await
+        && untracked_output.status.success()
+    {
+        let untracked: Vec<String> = String::from_utf8(untracked_output.stdout)
+            .ok()?
+            .lines()
+            .map(|s| s.to_string())
+            .filter(|s| !s.is_empty())
+            .collect();
+
+        if !untracked.is_empty() {
+            let futures_iter = untracked.into_iter().map(|file| async move {
+                let file_owned = file;
+                let args_vec: Vec<&str> =
+                    vec!["diff", "--binary", "--no-index", "/dev/null", &file_owned];
+                run_git_command_with_timeout(&args_vec, cwd).await
+            });
+            let results = join_all(futures_iter).await;
+            for extra in results.into_iter().flatten() {
+                if extra.status.code().is_some_and(|c| c == 0 || c == 1)
+                    && let Ok(s) = String::from_utf8(extra.stdout)
+                {
+                    diff.push_str(&s);
+                }
+            }
+        }
+    }
+
+    Some(diff)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -104,7 +435,8 @@ mod tests {
 
     // Helper function to create a test git repository
     async fn create_test_git_repo(temp_dir: &TempDir) -> PathBuf {
-        let repo_path = temp_dir.path().to_path_buf();
+        let repo_path = temp_dir.path().join("repo");
+        fs::create_dir(&repo_path).expect("Failed to create repo dir");
         let envs = vec![
             ("GIT_CONFIG_GLOBAL", "/dev/null"),
             ("GIT_CONFIG_NOSYSTEM", "1"),
@@ -159,6 +491,41 @@ mod tests {
         repo_path
     }
 
+    async fn create_test_git_repo_with_remote(temp_dir: &TempDir) -> (PathBuf, String) {
+        let repo_path = create_test_git_repo(temp_dir).await;
+        let remote_path = temp_dir.path().join("remote.git");
+
+        Command::new("git")
+            .args(["init", "--bare", remote_path.to_str().unwrap()])
+            .output()
+            .await
+            .expect("Failed to init bare remote");
+
+        Command::new("git")
+            .args(["remote", "add", "origin", remote_path.to_str().unwrap()])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to add remote");
+
+        let output = Command::new("git")
+            .args(["rev-parse", "--abbrev-ref", "HEAD"])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to get branch");
+        let branch = String::from_utf8(output.stdout).unwrap().trim().to_string();
+
+        Command::new("git")
+            .args(["push", "-u", "origin", &branch])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to push initial commit");
+
+        (repo_path, branch)
+    }
+
     #[tokio::test]
     async fn test_collect_git_info_non_git_directory() {
         let temp_dir = TempDir::new().expect("Failed to create temp dir");
@@ -272,6 +639,136 @@ mod tests {
         assert_eq!(git_info.branch, Some("feature-branch".to_string()));
     }
 
+    #[tokio::test]
+    async fn test_get_git_working_tree_state_clean_repo() {
+        let temp_dir = TempDir::new().expect("Failed to create temp dir");
+        let (repo_path, branch) = create_test_git_repo_with_remote(&temp_dir).await;
+
+        let remote_sha = Command::new("git")
+            .args(["rev-parse", &format!("origin/{branch}")])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to rev-parse remote");
+        let remote_sha = String::from_utf8(remote_sha.stdout)
+            .unwrap()
+            .trim()
+            .to_string();
+
+        let state = git_diff_to_remote(&repo_path)
+            .await
+            .expect("Should collect working tree state");
+        assert_eq!(state.sha, GitSha::new(&remote_sha));
+        assert!(state.diff.is_empty());
+    }
+
+    #[tokio::test]
+    async fn test_get_git_working_tree_state_with_changes() {
+        let temp_dir = TempDir::new().expect("Failed to create temp dir");
+        let (repo_path, branch) = create_test_git_repo_with_remote(&temp_dir).await;
+
+        let tracked = repo_path.join("test.txt");
+        fs::write(&tracked, "modified").unwrap();
+        fs::write(repo_path.join("untracked.txt"), "new").unwrap();
+
+        let remote_sha = Command::new("git")
+            .args(["rev-parse", &format!("origin/{branch}")])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to rev-parse remote");
+        let remote_sha = String::from_utf8(remote_sha.stdout)
+            .unwrap()
+            .trim()
+            .to_string();
+
+        let state = git_diff_to_remote(&repo_path)
+            .await
+            .expect("Should collect working tree state");
+        assert_eq!(state.sha, GitSha::new(&remote_sha));
+        assert!(state.diff.contains("test.txt"));
+        assert!(state.diff.contains("untracked.txt"));
+    }
+
+    #[tokio::test]
+    async fn test_get_git_working_tree_state_branch_fallback() {
+        let temp_dir = TempDir::new().expect("Failed to create temp dir");
+        let (repo_path, _branch) = create_test_git_repo_with_remote(&temp_dir).await;
+
+        Command::new("git")
+            .args(["checkout", "-b", "feature"])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to create feature branch");
+        Command::new("git")
+            .args(["push", "-u", "origin", "feature"])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to push feature branch");
+
+        Command::new("git")
+            .args(["checkout", "-b", "local-branch"])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to create local branch");
+
+        let remote_sha = Command::new("git")
+            .args(["rev-parse", "origin/feature"])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to rev-parse remote");
+        let remote_sha = String::from_utf8(remote_sha.stdout)
+            .unwrap()
+            .trim()
+            .to_string();
+
+        let state = git_diff_to_remote(&repo_path)
+            .await
+            .expect("Should collect working tree state");
+        assert_eq!(state.sha, GitSha::new(&remote_sha));
+    }
+
+    #[tokio::test]
+    async fn test_get_git_working_tree_state_unpushed_commit() {
+        let temp_dir = TempDir::new().expect("Failed to create temp dir");
+        let (repo_path, branch) = create_test_git_repo_with_remote(&temp_dir).await;
+
+        let remote_sha = Command::new("git")
+            .args(["rev-parse", &format!("origin/{branch}")])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to rev-parse remote");
+        let remote_sha = String::from_utf8(remote_sha.stdout)
+            .unwrap()
+            .trim()
+            .to_string();
+
+        fs::write(repo_path.join("test.txt"), "updated").unwrap();
+        Command::new("git")
+            .args(["add", "test.txt"])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to add file");
+        Command::new("git")
+            .args(["commit", "-m", "local change"])
+            .current_dir(&repo_path)
+            .output()
+            .await
+            .expect("Failed to commit");
+
+        let state = git_diff_to_remote(&repo_path)
+            .await
+            .expect("Should collect working tree state");
+        assert_eq!(state.sha, GitSha::new(&remote_sha));
+        assert!(state.diff.contains("updated"));
+    }
+
     #[test]
     fn test_git_info_serialization() {
         let git_info = GitInfo {

codex-rs/mcp-server/src/codex_message_processor.rs

@@ -8,11 +8,13 @@ use codex_core::ConversationManager;
 use codex_core::NewConversation;
 use codex_core::config::Config;
 use codex_core::config::ConfigOverrides;
+use codex_core::git_info::git_diff_to_remote;
 use codex_core::protocol::ApplyPatchApprovalRequestEvent;
 use codex_core::protocol::Event;
 use codex_core::protocol::EventMsg;
 use codex_core::protocol::ExecApprovalRequestEvent;
 use codex_core::protocol::ReviewDecision;
+use codex_protocol::mcp_protocol::GitDiffToRemoteResponse;
 use mcp_types::JSONRPCErrorError;
 use mcp_types::RequestId;
 use tokio::sync::Mutex;
@@ -126,6 +128,9 @@ impl CodexMessageProcessor {
             ClientRequest::CancelLoginChatGpt { request_id, params } => {
                 self.cancel_login_chatgpt(request_id, params.login_id).await;
             }
+            ClientRequest::GitDiffToRemote { request_id, params } => {
+                self.git_diff_to_origin(request_id, params.cwd).await;
+            }
         }
     }
 
@@ -514,6 +519,27 @@ impl CodexMessageProcessor {
             }
         }
     }
+
+    async fn git_diff_to_origin(&self, request_id: RequestId, cwd: PathBuf) {
+        let diff = git_diff_to_remote(&cwd).await;
+        match diff {
+            Some(value) => {
+                let response = GitDiffToRemoteResponse {
+                    sha: value.sha,
+                    diff: value.diff,
+                };
+                self.outgoing.send_response(request_id, response).await;
+            }
+            None => {
+                let error = JSONRPCErrorError {
+                    code: INVALID_REQUEST_ERROR_CODE,
+                    message: format!("failed to compute git diff to remote for cwd: {cwd:?}"),
+                    data: None,
+                };
+                self.outgoing.send_error(request_id, error).await;
+            }
+        }
+    }
 }
 
 async fn apply_bespoke_event_handling(

codex-rs/protocol-ts/src/lib.rs

@@ -36,6 +36,7 @@ pub fn generate_ts(out_dir: &Path, prettier: Option<&Path>) -> Result<()> {
     codex_protocol::mcp_protocol::LoginChatGptCompleteNotification::export_all_to(out_dir)?;
     codex_protocol::mcp_protocol::CancelLoginChatGptParams::export_all_to(out_dir)?;
     codex_protocol::mcp_protocol::CancelLoginChatGptResponse::export_all_to(out_dir)?;
+    codex_protocol::mcp_protocol::GitDiffToRemoteParams::export_all_to(out_dir)?;
     codex_protocol::mcp_protocol::ApplyPatchApprovalParams::export_all_to(out_dir)?;
     codex_protocol::mcp_protocol::ApplyPatchApprovalResponse::export_all_to(out_dir)?;
     codex_protocol::mcp_protocol::ExecCommandApprovalParams::export_all_to(out_dir)?;

codex-rs/protocol/src/mcp_protocol.rs

@@ -26,6 +26,16 @@ impl Display for ConversationId {
     }
 }
 
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, TS)]
+#[ts(type = "string")]
+pub struct GitSha(pub String);
+
+impl GitSha {
+    pub fn new(sha: &str) -> Self {
+        Self(sha.to_string())
+    }
+}
+
 /// Request from the client to the server.
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, TS)]
 #[serde(tag = "method", rename_all = "camelCase")]
@@ -69,6 +79,11 @@ pub enum ClientRequest {
         request_id: RequestId,
         params: CancelLoginChatGptParams,
     },
+    GitDiffToRemote {
+        #[serde(rename = "id")]
+        request_id: RequestId,
+        params: GitDiffToRemoteParams,
+    },
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Default, TS)]
@@ -139,6 +154,13 @@ pub struct LoginChatGptResponse {
     pub auth_url: String,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, TS)]
+#[serde(rename_all = "camelCase")]
+pub struct GitDiffToRemoteResponse {
+    pub sha: GitSha,
+    pub diff: String,
+}
+
 // Event name for notifying client of login completion or failure.
 pub const LOGIN_CHATGPT_COMPLETE_EVENT: &str = "codex/event/login_chatgpt_complete";
 
@@ -157,6 +179,12 @@ pub struct CancelLoginChatGptParams {
     pub login_id: Uuid,
 }
 
+#[derive(Serialize, Deserialize, Debug, Clone, PartialEq, TS)]
+#[serde(rename_all = "camelCase")]
+pub struct GitDiffToRemoteParams {
+    pub cwd: PathBuf,
+}
+
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, TS)]
 #[serde(rename_all = "camelCase")]
 pub struct CancelLoginChatGptResponse {}