cloud: default to current branch in cloud exec (#7460)

## Summary
- add a shared git-ref resolver and use it for `codex cloud exec` and
TUI task submission
- expose a new `--branch` flag to override the git ref passed to cloud
tasks
- cover the git-ref resolution behavior with new async unit tests and
supporting dev dependencies

## Testing
- cargo test -p codex-cloud-tasks


------
[Codex
Task](https://chatgpt.com/codex/tasks/task_i_692decc6cbec8332953470ef063e11ab)

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Jeremy Rose <172423086+nornagon-openai@users.noreply.github.com>
Co-authored-by: Jeremy Rose <nornagon@openai.com>

codex-rs/cloud-tasks/Cargo.toml

@@ -37,6 +37,9 @@ unicode-width = { workspace = true }
 owo-colors = { workspace = true, features = ["supports-colors"] }
 supports-color = { workspace = true }
 
+[dependencies.async-trait]
+workspace = true
+
 [dev-dependencies]
 async-trait = { workspace = true }
 pretty_assertions = { workspace = true }

codex-rs/cloud-tasks/src/cli.rs

@@ -34,10 +34,6 @@ pub struct ExecCommand {
     #[arg(long = "env", value_name = "ENV_ID")]
     pub environment: String,
 
-    /// Git branch to run in Codex Cloud.
-    #[arg(long = "branch", value_name = "BRANCH", default_value = "main")]
-    pub branch: String,
-
     /// Number of assistant attempts (best-of-N).
     #[arg(
         long = "attempts",
@@ -45,6 +41,10 @@ pub struct ExecCommand {
         value_parser = parse_attempts
     )]
     pub attempts: usize,
+
+    /// Git branch to run in Codex Cloud (defaults to current branch).
+    #[arg(long = "branch", value_name = "BRANCH")]
+    pub branch: Option<String>,
 }
 
 fn parse_attempts(input: &str) -> Result<usize, String> {

codex-rs/cloud-tasks/src/lib.rs

@@ -104,6 +104,54 @@ async fn init_backend(user_agent_suffix: &str) -> anyhow::Result<BackendContext>
     })
 }
 
+#[async_trait::async_trait]
+trait GitInfoProvider {
+    async fn default_branch_name(&self, path: &std::path::Path) -> Option<String>;
+
+    async fn current_branch_name(&self, path: &std::path::Path) -> Option<String>;
+}
+
+struct RealGitInfo;
+
+#[async_trait::async_trait]
+impl GitInfoProvider for RealGitInfo {
+    async fn default_branch_name(&self, path: &std::path::Path) -> Option<String> {
+        codex_core::git_info::default_branch_name(path).await
+    }
+
+    async fn current_branch_name(&self, path: &std::path::Path) -> Option<String> {
+        codex_core::git_info::current_branch_name(path).await
+    }
+}
+
+async fn resolve_git_ref(branch_override: Option<&String>) -> String {
+    resolve_git_ref_with_git_info(branch_override, &RealGitInfo).await
+}
+
+async fn resolve_git_ref_with_git_info(
+    branch_override: Option<&String>,
+    git_info: &impl GitInfoProvider,
+) -> String {
+    if let Some(branch) = branch_override {
+        let branch = branch.trim();
+        if !branch.is_empty() {
+            return branch.to_string();
+        }
+    }
+
+    if let Ok(cwd) = std::env::current_dir() {
+        if let Some(branch) = git_info.current_branch_name(&cwd).await {
+            branch
+        } else if let Some(branch) = git_info.default_branch_name(&cwd).await {
+            branch
+        } else {
+            "main".to_string()
+        }
+    } else {
+        "main".to_string()
+    }
+}
+
 async fn run_exec_command(args: crate::cli::ExecCommand) -> anyhow::Result<()> {
     let crate::cli::ExecCommand {
         query,
@@ -114,11 +162,12 @@ async fn run_exec_command(args: crate::cli::ExecCommand) -> anyhow::Result<()> {
     let ctx = init_backend("codex_cloud_tasks_exec").await?;
     let prompt = resolve_query_input(query)?;
     let env_id = resolve_environment_id(&ctx, &environment).await?;
+    let git_ref = resolve_git_ref(branch.as_ref()).await;
     let created = codex_cloud_tasks_client::CloudBackend::create_task(
         &*ctx.backend,
         &env_id,
         &prompt,
-        &branch,
+        &git_ref,
         false,
         attempts,
     )
@@ -1362,17 +1411,7 @@ pub async fn run_main(cli: Cli, _codex_linux_sandbox_exe: Option<PathBuf>) -> an
                                                 let backend = Arc::clone(&backend);
                                                 let best_of_n = page.best_of_n;
                                                 tokio::spawn(async move {
-                                                    let git_ref = if let Ok(cwd) = std::env::current_dir() {
+                                                    let git_ref = resolve_git_ref(None).await;
-                                                        if let Some(branch) = codex_core::git_info::default_branch_name(&cwd).await {
-                                                            branch
-                                                        } else if let Some(branch) = codex_core::git_info::current_branch_name(&cwd).await {
-                                                            branch
-                                                        } else {
-                                                            "main".to_string()
-                                                        }
-                                                    } else {
-                                                        "main".to_string()
-                                                    };
 
                                                     let result = codex_cloud_tasks_client::CloudBackend::create_task(&*backend, &env, &text, &git_ref, false, best_of_n).await;
                                                     let evt = match result {
@@ -1991,6 +2030,7 @@ fn pretty_lines_from_error(raw: &str) -> Vec<String> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::resolve_git_ref_with_git_info;
     use codex_cloud_tasks_client::DiffSummary;
     use codex_cloud_tasks_client::MockClient;
     use codex_cloud_tasks_client::TaskId;
@@ -2005,6 +2045,85 @@ mod tests {
     use ratatui::buffer::Buffer;
     use ratatui::layout::Rect;
 
+    struct StubGitInfo {
+        default_branch: Option<String>,
+        current_branch: Option<String>,
+    }
+
+    impl StubGitInfo {
+        fn new(default_branch: Option<String>, current_branch: Option<String>) -> Self {
+            Self {
+                default_branch,
+                current_branch,
+            }
+        }
+    }
+
+    #[async_trait::async_trait]
+    impl super::GitInfoProvider for StubGitInfo {
+        async fn default_branch_name(&self, _path: &std::path::Path) -> Option<String> {
+            self.default_branch.clone()
+        }
+
+        async fn current_branch_name(&self, _path: &std::path::Path) -> Option<String> {
+            self.current_branch.clone()
+        }
+    }
+
+    #[tokio::test]
+    async fn branch_override_is_used_when_provided() {
+        let git_ref = resolve_git_ref_with_git_info(
+            Some(&"feature/override".to_string()),
+            &StubGitInfo::new(None, None),
+        )
+        .await;
+
+        assert_eq!(git_ref, "feature/override");
+    }
+
+    #[tokio::test]
+    async fn trims_override_whitespace() {
+        let git_ref = resolve_git_ref_with_git_info(
+            Some(&"  feature/spaces  ".to_string()),
+            &StubGitInfo::new(None, None),
+        )
+        .await;
+
+        assert_eq!(git_ref, "feature/spaces");
+    }
+
+    #[tokio::test]
+    async fn prefers_current_branch_when_available() {
+        let git_ref = resolve_git_ref_with_git_info(
+            None,
+            &StubGitInfo::new(
+                Some("default-main".to_string()),
+                Some("feature/current".to_string()),
+            ),
+        )
+        .await;
+
+        assert_eq!(git_ref, "feature/current");
+    }
+
+    #[tokio::test]
+    async fn falls_back_to_current_branch_when_default_is_missing() {
+        let git_ref = resolve_git_ref_with_git_info(
+            None,
+            &StubGitInfo::new(None, Some("develop".to_string())),
+        )
+        .await;
+
+        assert_eq!(git_ref, "develop");
+    }
+
+    #[tokio::test]
+    async fn falls_back_to_main_when_no_git_info_is_available() {
+        let git_ref = resolve_git_ref_with_git_info(None, &StubGitInfo::new(None, None)).await;
+
+        assert_eq!(git_ref, "main");
+    }
+
     #[test]
     fn format_task_status_lines_with_diff_and_label() {
         let now = Utc::now();