export: split cmdutil.export() to single-file and maybe-multiple-files cases Porting "hg export" to formatter is a bit hard because cmdutil.export() may append to files if the fntemplate is specified. This patch splits the hard part from the trivial case.

export: remove unused argument 'rev' from _exportsingle()

export: do not start pager if output will be written to file A copy of 3b569745af6c.

formatter: carry opts to file-based formatters by basefm This makes it slightly easier to port "hg export" to formatter.