feat: add an updates card showing nvtable's package table

Moves the nvchecker/nvtable table the login shell printed onto the
dashboard, as a wide card at the bottom centre. bin/updates-sample.sh
caches `nvtable -C -E` every ten minutes and starts nvchecker, fully
detached, at most every 30 minutes. The widget parses the cache and
colours it in the board's language: installed behind upstream is
critical, a shipped .info behind is a warning, with nvtable's status
dots per row and a legend on the bottom line. The mouse wheel scrolls
rows that do not fit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/bin/updates-sample.sh b/bin/updates-sample.sh
new file mode 100755
index 0000000..0c9ee3a
--- /dev/null
+++ b/bin/updates-sample.sh
@@ -0,0 +1,39 @@
+#!/bin/bash
+# Sample nvtable's package-update table into a cache file, for
+# widgets/updates.lua. Replaces the table the login shell used to print.
+#
+# nvchecker itself is slow (one network request per stanza), so it is started
+# in the background at most every 30 minutes, fully detached: conky's execi
+# waits for stdout to close, and a child holding it would stall the dashboard.
+# nvtable then reads whatever results the last completed run left, so a fresh
+# nvchecker run shows up on the next sample.
+
+set -u
+
+CACHE_DIR="${XDG_CACHE_HOME:-$HOME/.cache}/udt"
+CACHE="$CACHE_DIR/updates.txt"
+STAMP="$CACHE_DIR/nvchecker.stamp"
+NVCHECK_EVERY=1800
+
+# conky launched from the compositor does not inherit the login shell's PATH.
+PATH="$HOME/bin:$HOME/.local/bin:$PATH"
+
+command -v nvtable >/dev/null || { echo "updates-sample: nvtable not found" >&2; exit 1; }
+
+mkdir -p "$CACHE_DIR"
+
+if command -v nvchecker >/dev/null; then
+    last=$(cat "$STAMP" 2>/dev/null || echo 0)
+    now=$(date +%s)
+    if (( now - ${last:-0} >= NVCHECK_EVERY )); then
+        echo "$now" > "$STAMP"
+        setsid nvchecker </dev/null >/dev/null 2>&1 &
+    fi
+fi
+
+TMP="$CACHE.tmp.$$"
+trap 'rm -f "$TMP"' EXIT
+
+# -C and -E: plain ASCII, which the widget parses and colours itself.
+# Keep the old cache when nvtable fails, rather than replacing it with nothing.
+nvtable -C -E > "$TMP" 2>/dev/null && mv -f "$TMP" "$CACHE"