397     """``follow([file])``

   398     An alias for ``::.`` (ancestors of the working copy's first parent).

   399     If a filename is specified, the history of the given file is followed,

   400     including copies.

   401     """

   402     # i18n: "follow" is a keyword

   403     l = getargs(x, 0, 1, _("follow takes no arguments or a filename"))

   404     p = repo['.'].rev()

   405     if l:

   406         x = getstring(l[0], "follow expected a filename")

   407         s = set(ctx.rev() for ctx in repo['.'][x].ancestors())

   408     else:

   409         s = set(repo.changelog.ancestors(p))

   410 

   411     s |= set([p])

   412     return [r for r in subset if r in s]

   413 

   414 def followfile(repo, subset, f):