fix(service): use default_branch for graph and reflog endpoints

- git_commit_graph: use default_branch when rev is None
- git_commit_graph_react: use default_branch when rev is None
- git_commit_reflog: fall back to default_branch when HEAD is detached

Fixes errors:
- reference 'refs/heads/master' not found (graph-react endpoint)
- HEAD has no name (reflog endpoint when HEAD is detached)

libs/service/git/commit.rs

@@ -1031,6 +1031,15 @@ impl AppService {
     ) -> Result<Vec<CommitReflogEntryResponse>, AppError> {
         let repo = self.utils_find_repo(namespace, repo_name, ctx).await?;
 
+        // If refname is None and HEAD is detached, fall back to default_branch
+        let refname = refname.or_else(|| {
+            if repo.default_branch.is_empty() {
+                None
+            } else {
+                Some(repo.default_branch.clone())
+            }
+        });
+
         let entries = git_spawn!(repo, domain -> {
             domain.reflog_entries(refname.as_deref())
         })?;
@@ -1064,7 +1073,13 @@ impl AppService {
         }
 
         let repo = self.utils_find_repo(namespace, repo_name, ctx).await?;
-        let rev_clone = query.rev.clone();
+        let rev_clone = query.rev.clone().or_else(|| {
+            if repo.default_branch.is_empty() {
+                None
+            } else {
+                Some(format!("refs/heads/{}", repo.default_branch))
+            }
+        });
         let limit = query.limit.unwrap_or(0);
 
         let graph = git_spawn!(repo, domain -> {
@@ -1112,7 +1127,13 @@ impl AppService {
         }
 
         let repo = self.utils_find_repo(namespace, repo_name, ctx).await?;
-        let rev_clone = query.rev.clone();
+        let rev_clone = query.rev.clone().or_else(|| {
+            if repo.default_branch.is_empty() {
+                None
+            } else {
+                Some(format!("refs/heads/{}", repo.default_branch))
+            }
+        });
         let limit = query.limit.unwrap_or(0);
 
         let (graph, refs_grouped) = git_spawn!(repo, domain -> {