fetch: change storage implementation

Instead of partitioning over YYYY/mm/dd, take the SHA256 of the URL and
partition over the first, second and tail bytes of it. It has the upside
of being more rsync-friendly and there is no longer a need to keep a
different file, "everything", to look up already retrieved URLs. Also
replace the "url" file with a "meta" file, organized as key=value,
currently holding URL and retrieval date.

bin/fetch.sh

@@ -44,20 +44,22 @@ shift $((OPTIND - 1))
 : ${ARCHIVE_BASEDIR:=~/tmp/archive}
 mkdir -p "$ARCHIVE_BASEDIR"
 
-everything=$ARCHIVE_BASEDIR/everything
-touch "$everything"
-
-dir=$ARCHIVE_BASEDIR/$(date +%Y/%m/%d)
-mkdir -p "$dir" || exit 1
-
 rc=0
 for url; do
 	sha=$(sha256 -qs "$url")
-	outdir=$dir/$sha
 
-	if grep -q "^$url\$" "$everything"; then
+	t=$sha
+	h0=${t%${t#??}}
+	t=${t#??}
+	h1=${t%${t#??}}
+	t=${t#??}
+	ht=$t
+
+	outdir=$ARCHIVE_BASEDIR/$h0/$h1/$ht
+
+	if [ -f "$outdir/file" ]; then
 		printf "%s: already fetched %s\n" "${0##*/}" "$url" >&2
-		printf "%s\n" "$ARCHIVE_BASEDIR"/*/*/*/"$sha"/file
+		printf "%s\n" "$outdir/file"
 		continue
 	fi
 
@@ -65,8 +67,8 @@ for url; do
 
 	{
 		fetch_cmd -o "$outdir/file" "$url" &&
-		    printf "%s\n" "$url" >"$outdir/url" &&
-		    printf "%s\n" "$url" >>"$everything" &&
+		    printf "%s=%s\n" \
+		    url "$url" date "$(date +%Y-%m-%d)" >"$outdir/meta" &&
 		    printf "%s\n" "$outdir/file"
 	} || rc=1
 done