--- a/mercurial/registrar.py	Sat May 13 17:53:55 2017 +0900
+++ b/mercurial/registrar.py	Sat Jan 09 23:07:20 2016 +0900
@@ -96,6 +96,51 @@
         """
         pass
 
+def command(table):
+    """Returns a function object to be used as a decorator for making commands.
+
+    This function receives a command table as its argument. The table should
+    be a dict.
+
+    The returned function can be used as a decorator for adding commands
+    to that command table. This function accepts multiple arguments to define
+    a command.
+
+    The first argument is the command name.
+
+    The options argument is an iterable of tuples defining command arguments.
+    See ``mercurial.fancyopts.fancyopts()`` for the format of each tuple.
+
+    The synopsis argument defines a short, one line summary of how to use the
+    command. This shows up in the help output.
+
+    The norepo argument defines whether the command does not require a
+    local repository. Most commands operate against a repository, thus the
+    default is False.
+
+    The optionalrepo argument defines whether the command optionally requires
+    a local repository.
+
+    The inferrepo argument defines whether to try to find a repository from the
+    command line arguments. If True, arguments will be examined for potential
+    repository locations. See ``findrepo()``. If a repository is found, it
+    will be used.
+    """
+    def cmd(name, options=(), synopsis=None, norepo=False, optionalrepo=False,
+            inferrepo=False):
+        def decorator(func):
+            func.norepo = norepo
+            func.optionalrepo = optionalrepo
+            func.inferrepo = inferrepo
+            if synopsis:
+                table[name] = func, list(options), synopsis
+            else:
+                table[name] = func, list(options)
+            return func
+        return decorator
+
+    return cmd
+
 class revsetpredicate(_funcregistrarbase):
     """Decorator to register revset predicate