Added time-keeping and kernel downloading

scripts/fetch-kernels.sh

@@ -0,0 +1,54 @@
+#!/bin/sh
+# Fetches the ANISE kernels listed in data/kernels.tsv and verifies their
+# checksums. Idempotent: a file that is already present and correct is left alone.
+#
+# Usage: scripts/fetch-kernels.sh [directory]
+#        ASTROKIT_KERNELS=/somewhere scripts/fetch-kernels.sh
+
+set -e
+
+root=$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)
+manifest="$root/data/kernels.tsv"
+target=${1:-${ASTROKIT_KERNELS:-$root/data/kernels}}
+
+if [ ! -f "$manifest" ]; then
+    echo "no manifest at $manifest" >&2
+    exit 1
+fi
+
+mkdir -p "$target"
+echo "kernels -> $target"
+
+status=0
+while IFS="$(printf '\t')" read -r name sha downloaded url purpose; do
+    case "$name" in '' | \#*) continue ;; esac
+
+    path="$target/$name"
+    if [ -f "$path" ] && [ "$(sha256sum "$path" | cut -d' ' -f1)" = "$sha" ]; then
+        echo "  ok       $name"
+        continue
+    fi
+
+    echo "  fetching $name  (pinned $downloaded)"
+    if ! curl -sfL --retry 3 -o "$path.partial" "$url"; then
+        echo "  FAILED   $name: could not download $url" >&2
+        rm -f "$path.partial"
+        status=1
+        continue
+    fi
+
+    got=$(sha256sum "$path.partial" | cut -d' ' -f1)
+    if [ "$got" != "$sha" ]; then
+        echo "  FAILED   $name: checksum mismatch" >&2
+        echo "             expected $sha" >&2
+        echo "             got      $got" >&2
+        rm -f "$path.partial"
+        status=1
+        continue
+    fi
+
+    mv "$path.partial" "$path"
+    echo "  verified $name"
+done < "$manifest"
+
+exit $status