Clarify precedence for template/style in commands.show_changeset():
Display format will be the first non-empty hit of:
1. option 'template'
2. option 'style'
3. [ui] setting 'logtemplate'
4. [ui] setting 'style'
If all of these values are either the unset or the empty string,
regular display via changeset_printer() is done.
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 = '#rawfileheader##raw#'
fileline = '#line#'
diffblock = '#lines#'
filediff = filediff-raw.tmpl
fileannotate = fileannotate-raw.tmpl
annotateline = '#author#@#rev#: #line#'