new sane-deadlines tool to remind me of upcoming deadlines

pkgs/sane-scripts/src/sane-deadlines

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+
+# processes a tab-separated "deadlines" file and alerts for any upcoming events.
+#
+# deadlines.tsv file format:
+# - <date>\t<event>
+# - no header
+# - one line per entry
+# - <event> may contain any non-newline and non-tab characters
+# - <date> should be lexicographically orderable and machine-parsable, e.g. `2023-03-14`
+#
+# example `deadlines.tsv`
+# 2023-03-14 celebrate pi day!
+# 2023-04-18 taxes due
+# 2023-04-01 the other pie day :o
+
+# configurables:
+deadlines=~/knowledge/planner/deadlines.tsv
+threshold_in_days=14  # only show events happening within this many days
+
+if ! test -f "$deadlines"; then
+        echo "WARNING: $deadlines sane-deadlines file not found"
+        exit 1
+fi
+
+today=$(date +%s)
+sort "$deadlines" | while read line; do
+        # parse line
+        date_field=$(echo "$line" | cut -f 1)
+        event=$(echo "$line" | cut -f 2)
+
+        # compute temporal distance
+        date=$(date -d "$date_field" +%s)
+        days_until=$(( ($date - $today) / (24*60*60) ))
+
+        # show the event iff it's near
+        if test "$days_until" -lt "$threshold_in_days"; then
+                echo "$days_until days until $event"
+        fi
+done