Move git utilities into a dedicated crate (#15564)

- create `codex-git-utils` and move the shared git helpers into it with
file moves preserved for diff readability
- move the `GitInfo` helpers out of `core` so stacked rollout work can
depend on the shared crate without carrying its own git info module

---------

Co-authored-by: Ahmed Ibrahim <219906144+aibrahim-oai@users.noreply.github.com>
Co-authored-by: Codex <noreply@openai.com>

codex-rs/app-server/Cargo.toml

@@ -34,6 +34,7 @@ codex-cloud-requirements = { workspace = true }
 codex-core = { workspace = true }
 codex-exec-server = { workspace = true }
 codex-features = { workspace = true }
+codex-git-utils = { workspace = true }
 codex-otel = { workspace = true }
 codex-shell-command = { workspace = true }
 codex-utils-cli = { workspace = true }

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

@@ -213,7 +213,6 @@ use codex_core::find_archived_thread_path_by_id_str;
 use codex_core::find_thread_name_by_id;
 use codex_core::find_thread_names_by_ids;
 use codex_core::find_thread_path_by_id_str;
-use codex_core::git_info::git_diff_to_remote;
 use codex_core::mcp::auth::discover_supported_scopes;
 use codex_core::mcp::auth::resolve_oauth_scopes;
 use codex_core::mcp::collect_mcp_snapshot;
@@ -243,6 +242,7 @@ use codex_features::FEATURES;
 use codex_features::Feature;
 use codex_features::Stage;
 use codex_feedback::CodexFeedback;
+use codex_git_utils::git_diff_to_remote;
 use codex_login::ServerOptions as LoginServerOptions;
 use codex_login::ShutdownHandle;
 use codex_login::auth::login_with_chatgpt_auth_tokens;
@@ -8224,7 +8224,7 @@ fn extract_conversation_summary(
 
 fn map_git_info(git_info: &CoreGitInfo) -> ConversationGitInfo {
     ConversationGitInfo {
-        sha: git_info.commit_hash.clone(),
+        sha: git_info.commit_hash.as_ref().map(|sha| sha.0.clone()),
         branch: git_info.branch.clone(),
         origin_url: git_info.repository_url.clone(),
     }

codex-rs/app-server/tests/suite/v2/thread_list.rs

@@ -23,6 +23,7 @@ use codex_app_server_protocol::TurnStartParams;
 use codex_app_server_protocol::TurnStartResponse;
 use codex_app_server_protocol::UserInput;
 use codex_core::ARCHIVED_SESSIONS_SUBDIR;
+use codex_git_utils::GitSha;
 use codex_protocol::ThreadId;
 use codex_protocol::protocol::GitInfo as CoreGitInfo;
 use codex_protocol::protocol::RolloutItem;
@@ -959,7 +960,7 @@ async fn thread_list_includes_git_info() -> Result<()> {
     create_minimal_config(codex_home.path())?;
 
     let git_info = CoreGitInfo {
-        commit_hash: Some("abc123".to_string()),
+        commit_hash: Some(GitSha::new("abc123")),
         branch: Some("main".to_string()),
         repository_url: Some("https://example.com/repo.git".to_string()),
     };

codex-rs/app-server/tests/suite/v2/thread_metadata_update.rs

@@ -20,6 +20,7 @@ use codex_app_server_protocol::ThreadStartResponse;
 use codex_app_server_protocol::ThreadStatus;
 use codex_core::ARCHIVED_SESSIONS_SUBDIR;
 use codex_core::state_db::reconcile_rollout;
+use codex_git_utils::GitSha;
 use codex_protocol::ThreadId;
 use codex_protocol::protocol::GitInfo as RolloutGitInfo;
 use codex_state::StateRuntime;
@@ -378,7 +379,7 @@ async fn thread_metadata_update_can_clear_stored_git_fields() -> Result<()> {
         "Thread preview",
         Some("mock_provider"),
         Some(RolloutGitInfo {
-            commit_hash: Some("abc123".to_string()),
+            commit_hash: Some(GitSha::new("abc123")),
             branch: Some("feature/sidebar-pr".to_string()),
             repository_url: Some("git@example.com:openai/codex.git".to_string()),
         }),