m: allow showing summary of directories in list

Add a PATH-like variable M_LIST_PATH. If no arguments are given and this
new variable isn't empty, show a summary of those directories, without
showing stats for each subdirectory. This permits a more compact output
that comes handy when your directory tree is growing out of control.

mblaze/m.sh

@@ -22,6 +22,36 @@ Usage:
 	exit 1
 }
 
+_mlist_i_rec_ln()
+{
+	if [ $# -eq 4 ]; then
+		printf "%6d unseen  %3d flagged  %6d msg  %s\n" "$@"
+	else
+		printf "%6d unseen  %3d flagged  %6d msg\n" "$@"
+	fi
+}
+
+_mlist_i_rec()
+{
+	tuc=0
+	tfc=0
+	tmc=0
+	entries=0
+	while IFS= read -r dir; do
+		mdirs "$dir" | mlist -i | tail -n 1 | {
+			IFS=" " read -r uc ut fc ft mc mt dummy
+			_mlist_i_rec_ln "$uc" "$fc" "$mc" "$dir"
+			tuc=$((tuc + uc))
+			tfc=$((tfc + fc))
+			tmc=$((tmc + mc))
+			entries=$((entries + 1))
+		}
+	done
+	if [ $entries -gt 1 ]; then
+		_mlist_i_rec_ln "$tuc" "$tfc" "$tmc"
+	fi
+}
+
 m_fetch_usage()
 {
 	printf "Usage: %s f|fetch\n" "${0##*/}" >&2
@@ -53,7 +83,18 @@ m_list()
 {
 	pwd=$(pwd)
 	# cut(1) lists are 1-based, and +1 for leading slash
-	mdirs "${@:-.}" | sort -t / | cut -c $((${#pwd} + 2))- | mlist -i
+	pwd_offset=$((${#pwd} + 2))
+	if [ $# -eq 0 ] && [ -n "$M_LIST_PATH" ]; then
+		oldIFS=$IFS
+		IFS=:
+		set -- $M_LIST_PATH
+		IFS=$oldIFS
+
+		printf "%s\n" "$@" | sort -t / | cut -c $pwd_offset- |
+		    _mlist_i_rec
+	else
+		mdirs "${@:-.}" | sort -t / | cut -c $pwd_offset- | mlist -i
+	fi
 }
 
 m_read()