hooks: add preupdate and update hooks.
preupdate run before working dir updated. can prevent update.
update run after working dir updated.
header = header-raw.tmpl
footer = ''
changeset = changeset-raw.tmpl
difflineplus = '#line#'
difflineminus = '#line#'
difflineat = '#line#'
diffline = '#line#'
changesetparent = '# parent: #node#'
changesetchild = '# child: #node#'
filenodelink = ''
filerevision = 'Content-Type: #mimetype#\nContent-Disposition: filename=#file#\n\n#raw#'
fileline = '#line#'
diffblock = '#lines#'
filediff = filediff-raw.tmpl
fileannotate = fileannotate-raw.tmpl
annotateline = '#author#@#rev#: #line#'