anchor.diff:  If you specify a cache file, then when *autorevision* is run where no
   repository can be recognized, the values from the cache file will be
   used instead.  If a repository can be recognized, the cache is
  -rewritten. This feature makes it possible for your build to run
  -from an unpacked tarball that includes the cache file.
  +rewritten. This feature makes it possible for your build to run from
  +an unpacked tarball that includes the cache file.
   
   === Valid Repository Types ===
   
  
positive.code: autorevision - extract current-revision metadata from version-control repositories
  
  == SYNOPSIS ==
  *autorevision* {*-t* <output-type> | *-s* <symbol>} [*-o* <cache-file> [*-f*]] [*-U*] [*-V*]
  
  == DESCRIPTION ==
  Extracts metadata about the head revision from your repository.
  
  This program is meant to be used by project build systems to extract
  properties that can be used in software version strings. It can emit
  source files containing variable and macro definitions suitable for
  use with C, C++, Java, sh, Python, Perl, Mac info.plist and other
  types of files (see below for the full list).
  
  The generated source is written to standard output.
  
  This program can normally be called from anywhere within a repository
  copy.  Under bzr the copy must be of a branch, not a full multibranch
  
negative.code: *VCS_BASENAME*::
  The basename of the directory root.  For most VCSes this will simply
  be the basename of the repository root directory.  For Subversion,
  *autorevision* will attempt to navigate up though trunk, branches, and
  tags directories to find the actual root.
  
  *VCS_NUM*::
  A count of revisions between the current one and the initial
  