Fossil Wrapper

#   interceptors' below for usage.)
#
# - If an interceptor returns an empty list, the wrapper is expected
#   to exit without calling Fossil, thereby fully intercepting the
#   query. Otherwise, it acts as a pre-processor: the returned list is
#   treated as a revised parameter list and will be supplied to
#   `fossil'.
#
#   rephrased: 
#      interceptor modifies `params' (the current command line arguments
#      of the `fsl' call) and returns the modified list which is then
#      used in further processing and the final call to `fossil'. if
#      the interceptor returns nothing, `fsl' exits immediately.
#      in this case the only performed actions are those executed
#      by the interceptor itself.
#

proc interceptor {command_spec body} {
    # cf. `apply' documentation: the anonymous function for `apply'
    # has to be specified in the form {args body namespace} where
    # `args' spefifies the formal arguments of the function. in the
    # present case `args' is identical to `params'. in the current setup
    # the `namespace' argument is apparently redundant and could be
    # ommitted:

    set fn [list {params} $body [uplevel 1 {namespace current}]]
    
    foreach command [triggers_for $command_spec] {
       # this loop sets up the dictionary `config::commands' whose
       # keys are the known interceptor commands and whose values are
       # the corresponding anonymous function definitions. note that each
       # alternate name in `commands_spec (e.g., a, ali, alias etc.)
       # generates a further entry (with identical value).
       dict set config::commands $command $fn
    }
}

proc intercept {params} {
    set command [first $params]
    if {[interceptor? $command]} {
        # here, the interceptor definition is retrieved from the
        # `commands' dictionary and used as the anonymous function
        # argument for `apply' (and `params' as its concrete argument). 
        set params [apply [dict get $config::commands $command] $params]
    }
    return $params
}

# --( Command triggers )------------------------------------------------

   # map this interceptor command to `fossil (g)diff'. actually, we use `di'
   # instead of `diff' since only the former will trigger the `diff' filter:
   regsub {^(g?d)f} $params {\1i} params

   # extract the revison number information from `params'. contrary to
   # `fossil' it is acceptable to omit blanks between `-r' and `n:m':


   set rgx { \-r[[:blank:]]*}
   set rgxrevnum {[[:digit:]]+(:[[:digit:]]+)?}
   set rgx $rgx$rgxrevnum

   # without `-r' argument we can return already:
   if {![regexp $rgx $params revarg]} {return $params}

   # translate rev. numbers to sha1 hashes and construct the 
   # required `diff' arguments:

      incr cnt
   } 

   #replace `-r n:m' by the constructed `diff' arguments: 
   regsub $revarg $params $from$to params
   return $params
}

# --( further procs )---------------------------------------------------

proc unwrapTimeline records {
#-----------------------------------------------------------------------
# unwrap `fossil timeline' output, putting each checkin on a single
# line. expected input: currently, a list of \n terminated lines.
# (maybe the \n should go away?). continuation lines belonging
# to the checkin message (including the trailing user/tags info)