add --man option and reduce output of --help option

Printing the full man page requires the perl-doc package. To avoid this
dependency, print the less verbose output containing only the synopsis
and the option list for the --help option and print the full output
(requiring perldoc) for the --man option.

coverage.sh

@@ -52,7 +52,7 @@ if [ ! -e shared/mmdebstrap ] || [ mmdebstrap -nt shared/mmdebstrap ]; then
 fi
 
 starttime=
-total=109
+total=110
 i=1
 
 print_header() {
@@ -233,7 +233,20 @@ cat << END > shared/test.sh
 #!/bin/sh
 set -eu
 export LC_ALL=C.UTF-8
-$CMD --help | grep --quiet SYNOPSIS
+$CMD --help | grep --quiet --fixed-strings 'mmdebstrap [OPTION...] [SUITE [TARGET [MIRROR...]]]'
+END
+if [ "$HAVE_QEMU" = "yes" ]; then
+	./run_qemu.sh
+else
+	./run_null.sh SUDO
+fi
+
+print_header "test --man"
+cat << END > shared/test.sh
+#!/bin/sh
+set -eu
+export LC_ALL=C.UTF-8
+$CMD --man | grep --quiet --fixed-strings 'mmdebstrap [OPTION...] [*SUITE* [*TARGET* [*MIRROR*...]]]'
 END
 if [ "$HAVE_QEMU" = "yes" ]; then
 	./run_qemu.sh

mmdebstrap

@@ -1852,7 +1852,8 @@ sub main() {
     my $logfile = undef;
     Getopt::Long::Configure ('default', 'bundling', 'auto_abbrev', 'ignore_case_always');
     GetOptions(
-	'h|help'   => sub { pod2usage(-exitval => 0, -verbose => 2) },
+	'h|help'   => sub { pod2usage(-exitval => 0, -verbose => 1) },
+	'man'      => sub { pod2usage(-exitval => 0, -verbose => 2) },
 	'version'  => sub { print STDOUT "mmdebstrap $VERSION\n"; exit 0; },
 	'components=s@' => \$options->{components},
 	'variant=s' => \$options->{variant},
@@ -2756,7 +2757,14 @@ require a double dash and may be abbreviated to uniqueness.
 
 =item B<-h,--help>
 
-Print this help text and exit.
+Print synopsis and options of this man page and exit.
+
+=item B<--man>
+
+Show the full man page as generated from Perl POD in a pager. This requires
+the perldoc program from the perl-doc package. This is the same as running:
+
+    pod2man /usr/bin/mmdebstrap | man -l -
 
 =item B<--version>