fix: fetch to refs/remotes/gitea/* instead of overwriting refs/heads/*

svn_mirror/gitea.py

@@ -116,9 +116,9 @@ def fetch_from_gitea(mirror: Mirror, ref: Optional[str] = None) -> bool:
     canonical = str(mirror.canonical_dir)
 
     if ref:
-        refspec = f"+{ref}:{ref}"
+        refspec = f"+{ref}:refs/remotes/gitea/{ref.removeprefix('refs/heads/')}"
     else:
-        refspec = "+refs/heads/*:refs/heads/*"
+        refspec = "+refs/heads/*:refs/remotes/gitea/*"
 
     logger.info("Fetching %s → canonical …", gitea_path)
     _git(
@@ -128,4 +128,44 @@ def fetch_from_gitea(mirror: Mirror, ref: Optional[str] = None) -> bool:
     )
 
     logger.debug("Fetch from Gitea complete")
+
+    # Fast-forward local branches from remote-tracking refs
+    if not ref:
+        _ff_local_branches(canonical)
+
     return True
+
+
+def _ff_local_branches(git_dir: str):
+    """Fast-forward ``refs/heads/*`` from ``refs/remotes/gitea/*``."""
+    out = _git("--git-dir", git_dir, "for-each-ref",
+               "--format=%(refname)", "refs/remotes/gitea/",
+               timeout=30, check=False)
+    for rt_ref in out.splitlines():
+        rt_ref = rt_ref.strip()
+        if not rt_ref:
+            continue
+        branch = rt_ref.removeprefix("refs/remotes/gitea/")
+        local_ref = f"refs/heads/{branch}"
+
+        # Check if local branch exists
+        local_hash = _git("--git-dir", git_dir, "rev-parse", "--verify",
+                          "--quiet", local_ref, timeout=15, check=False)
+        if not local_hash:
+            _git("--git-dir", git_dir, "update-ref", local_ref, rt_ref,
+                 timeout=15)
+            logger.debug("Created new branch %s from Gitea", local_ref)
+            continue
+
+        # Fast-forward if possible
+        rt_hash = _git("--git-dir", git_dir, "rev-parse", "--verify",
+                       rt_ref, timeout=15, check=False)
+        if not rt_hash or rt_hash == local_hash:
+            continue
+
+        base = _git("--git-dir", git_dir, "merge-base", local_hash, rt_ref,
+                     timeout=15, check=False)
+        if base == local_hash:
+            _git("--git-dir", git_dir, "update-ref", local_ref, rt_ref,
+                 timeout=15)
+            logger.debug("Fast-forward %s from Gitea", local_ref)