Scan line formatting
....................

   The name of the program that generates a listing of one line per
message is held in `mh-scan-prog' (default: `"scan"').  Unless this
variable contains an absolute pathname, it is assumed to be in the
`mh-progs' directory.  You may link another program to `scan' (see
`mh-profile'(5)) to produce a different type of listing.

   If you change the format of the scan lines you'll need to tell mh-e
how to parse the new format.  As you see, quite a lot of variables are
involved to do that.  The first variable has to do with pruning out
garbage.

`mh-valid-scan-line'
     This regular expression describes a valid scan line.  This is used
     to eliminate error messages that are occasionally produced by
     `inc' or `scan' (default: `"^ *[0-9]"').

   Next, two variables control how the message numbers are parsed.

`mh-msg-number-regexp'
     This regular expression is used to extract the message number from
     a scan line.  Note that the message number must be placed in quoted
     parentheses, (\\(...\\)), as in the default of `"^ *\\([0-9]+\\)"'.

`mh-msg-search-regexp'
     Given a message number (which is inserted in `%d'), this regular
     expression will match the scan line that it represents (default:
     `"^[^0-9]*%d[^0-9]"').

   Finally, there are a slew of variables that control how mh-e marks up
the scan lines.

`mh-cmd-note'
     Number of characters to skip over before inserting notation
     (default: 4).  Note how it relates to the following regular
     expressions.

`mh-deleted-msg-regexp'
     This regular expression describes deleted messages (default:
     `"^....D"').  See also `mh-note-deleted'.

`mh-refiled-msg-regexp'
     This regular expression describes refiled messages (default:
     `"^....\\^"').  See also `mh-note-refiled'.

`mh-cur-scan-msg-regexp'
     This regular expression matches the current message (default:
     `"^....\\+"').  See also `mh-note-cur'.

`mh-good-msg-regexp'
     This regular expression describes which messages should be shown
     when mh-e goes to the next or previous message.  Normally, deleted
     or refiled messages are skipped over (default: `"^....[^D^]"').

`mh-note-deleted'
     Messages that have been deleted to are marked by this string
     (default: `"D"').  See also `mh-deleted-msg-regexp'.

`mh-note-refiled'
     Messages that have been refiled are marked by this string (default:
     `"^"').  See also `mh-refiled-msg-regexp'.

`mh-note-copied'
     Messages that have been copied are marked by this string (default:
     `"C"').

`mh-note-cur'
     The current message (in MH, not in mh-e) is marked by this string
     (default: `"+"').  See also `mh-cur-scan-msg-regexp'.

`mh-note-repl'
     Messages that have been replied to are marked by this string
     (default: `"-"').

`mh-note-forw'
     Messages that have been forwarded are marked by this string
     (default: `"F"').

`mh-note-dist'
     Messages that have been redistributed are marked by this string
     (default: `"R"').

`mh-note-printed'
     Messages that have been printed are marked by this string (default:
     `"P"').

`mh-note-seq'
     Messages in a sequence are marked by this string (default: `"%"').