rdep: Store cache as .tar.lz4 or .tar to save space

Unpacked rdep cache can take around 100M.  Use a .tar.lz4 (6M) or .tar
(36M) instead (.xz is too slow).

Signed-off-by: Michał Górny <[email protected]>

Author: mgorny

README.rst

@@ -172,7 +172,7 @@ are ignored.  See example above.
 
 rdep
 ----
-Dependencies: wget
+Dependencies: wget, optionally tar, xz and lz4
 
 Accepts one or more cat/pns and prints their reverse dependencies.
 The data is fetched from qa-reports.g.o.  Typical usage::
@@ -184,6 +184,11 @@ all data and have it put into ``${TMPDIR:-/tmp}/mgorny-dev-scripts``::
 
     rdep-fetch-cache
 
+If lz4 is installed, the cache will be saved as a ``.tar.lz4`` archive
+for space- and performance-efficient lookup; otherwise it will be saved
+as uncompressed ``.tar``.  If ``bsdtar`` is installed, it will be used
+instead of ``tar`` as it supports fast reads.
+
 
 Bugzilla helpers
 ================

rdep

@@ -1,12 +1,36 @@
 #!/bin/sh
 # print revdeps of packages specified on command-line
 
-fetch() {
-	if [ -d "${TMPDIR:-/tmp}"/mgorny-dev-scripts/${1}index ]; then
-		cat "${TMPDIR:-/tmp}"/mgorny-dev-scripts/${1}index/${pkg}
-	else
-		wget -q -O - https://qa-reports.gentoo.org/output/genrdeps/${1}index/${pkg}
+# bsdtar is faster than GNU tar
+if command -v bsdtar >/dev/null; then
+	TAR="bsdtar -xqOf"
+else
+	TAR="tar -xOf"
+fi
+
+# find the best cache available
+CACHEDIR=${TMPDIR:-/tmp}/mgorny-dev-scripts
+GET=
+if [ -d "${CACHEDIR}" ]; then
+	cd "${CACHEDIR}" || exit 1
+	if [ -f rdeps.tar.lz4 ]; then
+		GET="${TAR} rdeps.tar.lz4 "
+	elif [ -f rdeps.tar ]; then
+		GET="${TAR} rdeps.tar "
+	elif [ -d rindex ]; then
+		GET="cat "
 	fi
+fi
+
+# use wget if no cache available
+if [ -z "${GET}" ]; then
+	echo "[Fetching from qa-reports, please consider running rdep-fetch-cache]" >&2
+	GET="wget -q -O - https://qa-reports.gentoo.org/output/genrdeps/"
+fi
+
+
+fetch() {
+	${GET}${1}index/${pkg}
 }
 
 for pkg; do

rdep-fetch-cache

@@ -1,7 +1,17 @@
 #!/bin/sh
 # fetch cache for rdep
 
-mkdir -p "${TMPDIR:-/tmp}"/mgorny-dev-scripts &&
-cd "${TMPDIR:-/tmp}"/mgorny-dev-scripts &&
-exec wget -O - https://qa-reports.gentoo.org/output/genrdeps/rdeps.tar.xz |
-	tar -xJ
+mkdir -p "${TMPDIR:-/tmp}"/mgorny-dev-scripts || exit 1
+cd "${TMPDIR:-/tmp}"/mgorny-dev-scripts || exit 1
+
+if command -v lz4 >/dev/null; then
+	echo "lz4 available, repacking as rdeps.tar.lz4" >&2
+
+	exec wget -O - https://qa-reports.gentoo.org/output/genrdeps/rdeps.tar.xz |
+		xz -cd | lz4 -c > rdeps.tar.lz4
+else
+	echo "fetching to rdeps.tar (install lz4 to compress)" >&2
+
+	exec wget -O - https://qa-reports.gentoo.org/output/genrdeps/rdeps.tar.xz |
+		xz -cd > rdeps.tar
+fi