fix: avoid spawning git for branch lookup

1 files changed, 71 insertions, 16 deletions

diff --git a/src/workspace.rs b/src/workspace.rs
index 9a679040..02f971b0 100644
--- a/src/workspace.rs
+++ b/src/workspace.rs
@@ -686,26 +686,31 @@ pub fn derive_label_from_cwd(cwd: &Path) -> String {
 }
 
 pub fn git_branch(cwd: &Path) -> Option<String> {
-    git_repo_root(cwd)?;
-
-    let output = std::process::Command::new("git")
-        .arg("-C")
-        .arg(cwd)
-        .args(["rev-parse", "--abbrev-ref", "HEAD"])
-        .output()
-        .ok()?;
+    let repo_root = git_repo_root(cwd)?;
+    let git_dir = git_dir_for_repo_root(&repo_root)?;
+    let head = std::fs::read_to_string(git_dir.join("HEAD")).ok()?;
+    parse_git_head_branch(&head)
+}
 
-    if !output.status.success() {
-        return None;
+fn git_dir_for_repo_root(repo_root: &Path) -> Option<PathBuf> {
+    let git_path = repo_root.join(".git");
+    if git_path.is_dir() {
+        return Some(git_path);
     }
 
-    let stdout = String::from_utf8(output.stdout).ok()?;
-    let branch = stdout.trim();
-    if branch.is_empty() || branch == "HEAD" {
-        None
+    let gitdir = std::fs::read_to_string(&git_path).ok()?;
+    let relative = gitdir.trim().strip_prefix("gitdir:")?.trim();
+    let resolved = Path::new(relative);
+    Some(if resolved.is_absolute() {
+        resolved.to_path_buf()
     } else {
-        Some(branch.to_string())
-    }
+        repo_root.join(resolved)
+    })
+}
+
+fn parse_git_head_branch(head: &str) -> Option<String> {
+    let branch = head.trim().strip_prefix("ref: refs/heads/")?;
+    (!branch.is_empty()).then(|| branch.to_string())
 }
 
 fn git_repo_root(start: &Path) -> Option<PathBuf> {
@@ -833,6 +838,21 @@ mod tests {
     use super::*;
     use crate::detect::{Agent, AgentState};
 
+    fn temp_test_dir(name: &str) -> PathBuf {
+        let unique = format!(
+            "herdr-workspace-tests-{}-{}-{}",
+            name,
+            std::process::id(),
+            SystemTime::now()
+                .duration_since(UNIX_EPOCH)
+                .unwrap()
+                .as_nanos()
+        );
+        let path = std::env::temp_dir().join(unique);
+        std::fs::create_dir_all(&path).unwrap();
+        path
+    }
+
     #[test]
     fn aggregate_state_all_unknown() {
         let ws = Workspace::test_new("test");
@@ -893,6 +913,41 @@ mod tests {
     }
 
     #[test]
+    fn git_branch_reads_head_from_standard_repo() {
+        let root = temp_test_dir("standard-repo");
+        std::fs::create_dir_all(root.join(".git")).unwrap();
+        std::fs::write(root.join(".git/HEAD"), "ref: refs/heads/main\n").unwrap();
+
+        assert_eq!(git_branch(&root).as_deref(), Some("main"));
+
+        std::fs::remove_dir_all(root).unwrap();
+    }
+
+    #[test]
+    fn git_branch_reads_head_from_worktree_gitdir_file() {
+        let root = temp_test_dir("worktree");
+        let worktree_git_dir = root.join(".bare/worktrees/feature");
+        std::fs::create_dir_all(&worktree_git_dir).unwrap();
+        std::fs::write(root.join(".git"), "gitdir: .bare/worktrees/feature\n").unwrap();
+        std::fs::write(worktree_git_dir.join("HEAD"), "ref: refs/heads/feature\n").unwrap();
+
+        assert_eq!(git_branch(&root).as_deref(), Some("feature"));
+
+        std::fs::remove_dir_all(root).unwrap();
+    }
+
+    #[test]
+    fn git_branch_returns_none_for_detached_head() {
+        let root = temp_test_dir("detached-head");
+        std::fs::create_dir_all(root.join(".git")).unwrap();
+        std::fs::write(root.join(".git/HEAD"), "3e1b9a8d\n").unwrap();
+
+        assert_eq!(git_branch(&root), None);
+
+        std::fs::remove_dir_all(root).unwrap();
+    }
+
+    #[test]
     fn pane_details_hide_plain_shells() {
         let mut ws = Workspace::test_new("test");
         let root_pane = ws.tabs[0].root_pane;