mercurial: improve lookup logic and chained exceptions that can happen during that operation.

vcsserver/hgcompat.py

@@ -74,15 +74,19 b' from mercurial import strip as hgext_str'
 def get_ctx(repo, ref):
     if not isinstance(ref, int):
         ref = safe_bytes(ref)
+
     try:
         ctx = repo[ref]
+        return ctx
     except (ProgrammingError, TypeError):
         # we're unable to find the rev using a regular lookup, we fallback
         # to slower, but backward compat revsymbol usage
-        ctx = revsymbol(repo, ref)
+        pass
     except (LookupError, RepoLookupError):
         # Similar case as above but only for refs that are not numeric
         if isinstance(ref, int):
             raise
-        ctx = revsymbol(repo, ref)
+
+    ctx = revsymbol(repo, ref)
+
     return ctx