M1 R5: remote_head_sha via gix rev_parse_single (qwen2.5-coder:32b)

src/python.rs

@@ -75,8 +75,10 @@ fn head_sha(path: String) -> PyResult<Option<String>> {
 }
 
 #[pyfunction]
-fn remote_head_sha(_path: String, _remote_ref: String) -> PyResult<Option<String>> {
-    todo!("repo::remote_head_sha (resolve remote-tracking ref)")
+#[pyo3(signature = (path, remote_ref="origin/main".to_string()))]
+fn remote_head_sha(path: String, remote_ref: String) -> PyResult<Option<String>> {
+    // soft-fail: any error -> None (API.md)
+    Ok(crate::repo::remote_head_sha(std::path::Path::new(&path), &remote_ref).unwrap_or(None))
 }
 
 #[pyfunction]

src/repo/mod.rs

@@ -32,6 +32,9 @@ pub use current_branch::current_branch;
 mod tracking_branch;
 pub use tracking_branch::tracking_branch;
 
+mod remote_head_sha;
+pub use remote_head_sha::remote_head_sha;
+
 /// Temp-dir git fixtures shared by the per-method parity tests.
 ///
 /// Fixtures are built with the real `git` CLI, so each parity test asserts

src/repo/remote_head_sha.rs

@@ -0,0 +1,47 @@
+use crate::error::GitxtendError;
+use crate::repo::Result;
+use std::path::Path;
+
+/// Object id (full hex) that a remote-tracking ref resolves to, e.g.
+/// "origin/main"; `Ok(None)` if that ref doesn't exist. Mirrors
+/// `git rev-parse <remote_ref>`.
+pub fn remote_head_sha(path: &Path, remote_ref: &str) -> Result<Option<String>> {
+    let repo = gix::open(path).map_err(GitxtendError::from_err)?;
+    match repo.rev_parse_single(remote_ref) {
+        Ok(id) => Ok(Some(id.detach().to_string())),
+        Err(_) => Ok(None),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::repo::fixtures;
+    use tempfile::tempdir;
+
+    #[test]
+    fn no_such_remote_ref() {
+        let td = fixtures::repo();
+        let p = td.path();
+        assert_eq!(remote_head_sha(p, "origin/main").unwrap(), None);
+    }
+
+    #[test]
+    fn with_a_remote() {
+        let remote = tempdir().unwrap();
+        fixtures::git(remote.path(), &["init", "--bare", "-q", "-b", "main"]);
+        let td = fixtures::repo();
+        let p = td.path();
+        fixtures::git(
+            p,
+            &["remote", "add", "origin", &remote.path().to_string_lossy()],
+        );
+        fixtures::write(p, "file.txt", "content");
+        fixtures::git(p, &["add", "-A"]);
+        fixtures::git(p, &["commit", "-m", "initial commit"]);
+        fixtures::git(p, &["push", "-q", "-u", "origin", "main"]);
+
+        let expected = fixtures::git(p, &["rev-parse", "origin/main"]);
+        assert_eq!(remote_head_sha(p, "origin/main").unwrap(), Some(expected));
+    }
+}