custom link formatting

hi,

i'm looking for to add custom patterns to commit message formatters that could link to some external systems (bugtracker, wiki, etc)

here's sample how http://www.viewvc.org/ has it configurable (python syntax):

## custom_log_formatting: Specifies mappings of regular expressions to
## substitution format strings used to URL-ize strings found in
## revision log messages.  Multiple mappings (specified as
## REGEXP:FORMATSTRING) may be defined, separated by commas.
##
## NOTE: Due to a limitation of the configuration format, commas may
## not be used in the regular expression portion of each mapping.
## Commas "in the raw" may not be used in the format string portion,
## either, but you can probably use the URI-encoded form of the comma
## ("%2C") instead with no ill side-effects.  If you must specify a
## colon character in either the regular expression or the format
## string, escape it with a preceding backslash ("\:").
##
## Example:
## custom_log_formatting =
##     artf[0-9]+ : http://example.com/tracker?id=\0,
##     issue ([0-9]+) : http://example.com/bug?id=\1&opts=full%2csortby=id
##