fix: reject oversized git ref files in workspace status reads (#3373)

* fix: reject oversized git ref files in workspace status reads

refs #3343

* fix: treat oversized loose refs as unavailable instead of absent

refs #3343

* fix: classify git ref read errors instead of probing path existence

A loose ref behind a metadata or I/O error (for example an unsearchable
refs/heads directory) previously read as absent, because Path::exists()
also returns false on metadata errors, letting a stale same-name
packed-refs OID enter the workspace status fingerprint. The reader now
classifies the open error itself: NotFound and NotADirectory mean the
loose ref is absent (packed-refs fallback stays legitimate), every other
error marks the ref unavailable with no fallback. This also removes the
racy second existence probe.

refs #3343

* fix: reject empty loose git refs

refs #3343

* fix: reject dangling loose git refs

refs #3343

* fix: reject dangling git refs with invalid target paths

refs #3343

1 files changed, 3 insertions, 2 deletions

diff --git a/src/workspace/git/status.rs b/src/workspace/git/status.rs
index 4fb2b887..9f40170c 100644
--- a/src/workspace/git/status.rs
+++ b/src/workspace/git/status.rs
@@ -8,7 +8,8 @@ use super::{
     discovery::{
         automatic_workspace_label, canonicalize_best_effort_path, fallback_label_from_cwd,
         git_ref_storage_is_reftable, git_rev_parse_verify, git_space_metadata_from_info,
-        git_symbolic_head_full, git_worktree_info, read_ref_oid, GitWorktreeInfo,
+        git_symbolic_head_full, git_worktree_info, read_git_ref_file, read_ref_oid,
+        GitWorktreeInfo,
     },
 };
 
@@ -273,7 +274,7 @@ fn read_head_identity_from_git(info: &GitWorktreeInfo) -> Option<GitHeadIdentity
 }
 
 fn read_head_identity_from_files(info: &GitWorktreeInfo) -> Option<GitHeadIdentity> {
-    let head = std::fs::read_to_string(info.git_dir.join("HEAD")).ok()?;
+    let head = read_git_ref_file(&info.git_dir.join("HEAD"))?;
     let head = head.trim();
     if let Some(full_ref) = head.strip_prefix("ref: ") {
         let short_name = full_ref.strip_prefix("refs/heads/")?.to_string();