[Gnu-arch-users] [BUG] feature plan -- version variables

[Tom Lord]

Version variables are persistent variables associated 
with versions.  At each revision within a version, all
of the variables have a definate value.  By default, 
each revision inherits the values from its immediate ancestor
but variable values can be changed by any revision.


* Range

  The value of a version variable must be a Pika Scheme s-expression
  satisfying certain constraints:

        1) Only cons pairs, booleans, small integers,
           nil, and strings containing only iso-8859-1
           characters may occur in the value.

        2) Cons pairs may occur in the value only
           as part of a proper list.


* Domain

  The name of a version variable must consist entirely of ascii
  numbers and letters, dash ('-'), and dot ('.').  


* Representation

  Within a project tree, variable values are usually found by
  reading the patch-log.   The latest patch-log entry for the 
  tree-version of the project tree may contain a header:

        set-in-version: (<name> <value>)*

  Variables without an explicitly set value have the value false
  (`#f').

  If the file ./{arch}/++variables exists then it should contain
  0 or more valid `set-in-version' log message headers -- these
  override the settings in the latest patch log entry.


* Commands

  % tla version-var [--local|default|inherited]

  [print a list of version variables and their values

   --local: show only variables set in ./{arch}/++variables

   --inherited: show only variables set _only_ in the latest patch log
      entry

   --default: show all variables set in the latest patch log]


  % tla version-var name
  [print the value of name]

  % tla version-var name value
  [locally set the value of name to value]

  % tla version-var --unset name
  [remove any local setting for name]


-t

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