notmuch-{dump,restore}.1: document new format options

More or less arbitrarily, notmuch-dump.1 gets the more detailed
description of the format.

man/man1/notmuch-dump.1

@@ -5,6 +5,7 @@ notmuch-dump \- creates a plain-text dump of the tags of each message
 .SH SYNOPSIS
 
 .B "notmuch dump"
+.RB  [ "\-\-format=(sup|batch-tag)"  "] [--]"
 .RI "[ --output=<" filename "> ] [--]"
 .RI "[ <" search-term ">...]"
 
@@ -19,6 +20,64 @@ recreated from the messages themselves.  The output of notmuch dump is
 therefore the only critical thing to backup (and much more friendly to
 incremental backup than the native database files.)
 
+.TP 4
+.B \-\-format=(sup|batch-tag)
+
+Notmuch restore supports two plain text dump formats, both with one message-id
+per line, followed by a list of tags.
+
+.RS 4
+.TP 4
+.B sup
+
+The
+.B sup
+dump file format is specifically chosen to be
+compatible with the format of files produced by sup-dump.
+So if you've previously been using sup for mail, then the
+.B "notmuch restore"
+command provides you a way to import all of your tags (or labels as
+sup calls them).
+Each line has the following form
+
+.RS 4
+.RI < message-id >
+.B (
+.RI < tag "> ..."
+.B )
+
+with zero or more tags are separated by spaces. Note that (malformed)
+message-ids may contain arbitrary non-null characters. Note also
+that tags with spaces will not be correctly restored with this format.
+
+.RE
+
+.RE
+.RS 4
+.TP 4
+.B batch-tag
+
+The
+.B batch-tag
+dump format is intended to more robust against malformed message-ids
+and tags containing whitespace or non-\fBascii\fR(7) characters.
+Each line has the form
+
+.RS 4
+.RI "+<" "encoded-tag" "> " "" "+<" "encoded-tag" "> ... -- " "" " id:<" encoded-message-id >
+
+where encoded means that every byte not matching the regex
+.B [A-Za-z0-9@=.,_+-]
+is replace by
+.B %nn
+where nn is the two digit hex encoding.
+The astute reader will notice this is a special case of the batch input
+format for \fBnotmuch-tag\fR(1); note that the single message-id query is
+mandatory for \fBnotmuch-restore\fR(1).
+
+.RE
+
+
 With no search terms, a dump of all messages in the database will be
 generated.  A "--" argument instructs notmuch that the
 remaining arguments are search terms.

man/man1/notmuch-restore.1

@@ -6,6 +6,7 @@ notmuch-restore \- restores the tags from the given file (see notmuch dump)
 
 .B "notmuch restore"
 .RB [ "--accumulate" ]
+.RB [ "--format=(auto|batch-tag|sup)" ]
 .RI "[ --input=<" filename "> ]"
 
 .SH DESCRIPTION
@@ -15,19 +16,51 @@ Restores the tags from the given file (see
 
 The input is read from the given filename, if any, or from stdin.
 
-Note: The dump file format is specifically chosen to be
+
+Supported options for
+.B restore
+include
+.RS 4
+.TP 4
+.B \-\-accumulate
+
+The union of the existing and new tags is applied, instead of
+replacing each message's tags as they are read in from the dump file.
+
+.RE
+.RS 4
+.TP 4
+.B \-\-format=(sup|batch-tag|auto)
+
+Notmuch restore supports two plain text dump formats, with each line
+specifying a message-id and a set of tags.
+For details of the actual formats, see \fBnotmuch-dump\fR(1).
+
+.RS 4
+.TP 4
+.B sup
+
+The
+.B sup
+dump file format is specifically chosen to be
 compatible with the format of files produced by sup-dump.
 So if you've previously been using sup for mail, then the
 .B "notmuch restore"
 command provides you a way to import all of your tags (or labels as
 sup calls them).
 
-The --accumulate switch causes the union of the existing and new tags to be
-applied, instead of replacing each message's tags as they are read in from the
-dump file.
+.RE
+.RS 4
+.TP 4
+.B batch-tag
 
-See \fBnotmuch-search-terms\fR(7)
-for details of the supported syntax for <search-terms>.
+The
+.B batch-tag
+dump format is intended to more robust against malformed message-ids
+and tags containing whitespace or non-\fBascii\fR(7) characters.  This
+format hex-escapes all characters those outside of a small character
+set, intended to be suitable for e.g. pathnames in most UNIX-like
+systems.
 
 .B "notmuch restore"
 updates the maildir flags according to tag changes if the
@@ -36,6 +69,20 @@ configuration option is enabled. See \fBnotmuch-config\fR(1) for
 details.
 
 .RE
+
+.RS 4
+.TP 4
+.B auto
+
+This option (the default) tries to guess the format from the
+input. For correctly formed input in either supported format, this
+heuristic, based the fact that batch-tag format contains no parentheses,
+should be accurate.
+
+.RE
+
+.RE
+
 .SH SEE ALSO
 
 \fBnotmuch\fR(1), \fBnotmuch-config\fR(1), \fBnotmuch-count\fR(1),