From ac4690cc4bc1ff418ac58f4d567f1db75387be46 Mon Sep 17 00:00:00 2001
From: Shawn Hartsock <hartsock@users.noreply.github.com>
Date: Sun, 31 May 2026 11:49:16 -0400
Subject: [PATCH] M1 R3: current_branch via gix head.referent_name()
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src/repo/current_branch.rs — `current_branch(path) -> Result<Option<String>>` returns the short current-branch name (`Ok(None)` on detached HEAD) via gix `head.referent_name().shorten()`; registered + wired through the soft-fail PyO3 wrapper. Parity-tested vs `git rev-parse --abbrev-ref HEAD` plus a detached-HEAD case.

PROVENANCE: implementation + tests written by the local model qwen2.5-coder:32b, driven
headlessly through `newt worker` (newt-agent's ACP worker) by the pilot, which
applied the module registration + PyO3 wrapper wiring and any clippy fixups.

Co-Authored-By: qwen2.5-coder:32b <model@newt.local>
Model: qwen2.5-coder:32b
Piloted-by: newt-agent
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 src/python.rs              |  5 +++--
 src/repo/current_branch.rs | 38 ++++++++++++++++++++++++++++++++++++++
 src/repo/mod.rs            |  3 +++
 3 files changed, 44 insertions(+), 2 deletions(-)
 create mode 100644 src/repo/current_branch.rs

diff --git a/src/python.rs b/src/python.rs
index ecc15fd..c041bad 100644
--- a/src/python.rs
+++ b/src/python.rs
@@ -57,8 +57,9 @@ fn is_clean(_path: String) -> PyResult<bool> {
 }
 
 #[pyfunction]
-fn current_branch(_path: String) -> PyResult<Option<String>> {
-    todo!("repo::current_branch (None if detached)")
+fn current_branch(path: String) -> PyResult<Option<String>> {
+    // soft-fail: any error -> None (API.md)
+    Ok(crate::repo::current_branch(std::path::Path::new(&path)).unwrap_or(None))
 }
 
 #[pyfunction]
diff --git a/src/repo/current_branch.rs b/src/repo/current_branch.rs
new file mode 100644
index 0000000..09630c8
--- /dev/null
+++ b/src/repo/current_branch.rs
@@ -0,0 +1,38 @@
+use crate::error::GitxtendError;
+use crate::repo::Result;
+use std::path::Path;
+
+/// Short name of the current branch (e.g. "main"); `Ok(None)` when HEAD is
+/// detached (mirrors `git rev-parse --abbrev-ref HEAD`, which prints "HEAD"
+/// when detached — we return None in that case).
+pub fn current_branch(path: &Path) -> Result<Option<String>> {
+    let repo = gix::open(path).map_err(GitxtendError::from_err)?;
+    let head = repo.head().map_err(GitxtendError::from_err)?;
+    Ok(head.referent_name().map(|n| n.shorten().to_string()))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::repo::fixtures;
+
+    #[test]
+    fn test_current_branch_on_main() {
+        let td = fixtures::repo();
+        let p = td.path();
+        assert_eq!(current_branch(p).unwrap(), Some("main".into()));
+        assert_eq!(
+            current_branch(p).unwrap(),
+            Some(fixtures::git(p, &["rev-parse", "--abbrev-ref", "HEAD"]))
+        );
+    }
+
+    #[test]
+    fn test_current_branch_detached_head() {
+        let td = fixtures::repo();
+        let p = td.path();
+        let sha = fixtures::git(p, &["rev-parse", "HEAD"]);
+        fixtures::git(p, &["checkout", "--detach", &sha]);
+        assert_eq!(current_branch(p).unwrap(), None);
+    }
+}
diff --git a/src/repo/mod.rs b/src/repo/mod.rs
index 994d8d4..d14428f 100644
--- a/src/repo/mod.rs
+++ b/src/repo/mod.rs
@@ -26,6 +26,9 @@ pub use is_git_repo::is_git_repo;
 mod head_sha;
 pub use head_sha::head_sha;
 
+mod current_branch;
+pub use current_branch::current_branch;
+
 /// Temp-dir git fixtures shared by the per-method parity tests.
 ///
 /// Fixtures are built with the real `git` CLI, so each parity test asserts