diffs: limit commit line context to MAX_DIFF to prevent packetOverflow errors.

rhodecode/apps/repository/views/repo_commits.py

@@ -109,7 +109,7 b' def get_line_ctx(fid, request):'
         retval = ln_ctx_global
 
     try:
-        return int(retval)
+        return min(diffs.MAX_CONTEXT, int(retval))
     except Exception:
         return 3