grab.sh: Try and download a matched stage3/snapshot pair

Catalyst's autobuilds have been flaky recently, so it's a bit
difficult to predict when the next amd64 stage3 will land.  The
mirrors only keep a week of history, so it's easier to get the
stage3/snapshot pair from the same day if you try to grab them
automatically every evening.  This script will do that, using the
latest-stage3.txt to find the most recent stage3, and then downloading
the auxilliary files and Portage snapshot.  If the downloads all
succeed, it updates the default DATE in build.sh.

diff --git a/grab.sh b/grab.sh
new file mode 100755 (executable)
index 0000000..2fa636c
--- /dev/null
+++ b/grab.sh
@@ -0,0 +1,65 @@
+#!/bin/sh
+#
+# Copyright (C) 2014 W. Trevor King <wking@tremily.us>
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice, this
+# list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+
+MIRROR="${MIRROR:-http://distfiles.gentoo.org/}"
+BASE_ARCH_URL="${BASE_ARCH_URL:-${MIRROR}releases/amd64/autobuilds/}"
+LATEST=$(wget -O - "${BASE_ARCH_URL}latest-stage3.txt")
+DATE=$(echo "${LATEST}" | sed -n 's|/stage3-amd64-[0-9]*[.]tar[.]bz2||p')
+ARCH_URL="${ARCH_URL:-${BASE_ARCH_URL}${DATE}/}"
+STAGE3="${STAGE3:-stage3-amd64-${DATE}.tar.bz2}"
+STAGE3_CONTENTS="${STAGE3_CONTENTS:-${STAGE3}.CONTENTS}"
+STAGE3_DIGESTS="${STAGE3_DIGESTS:-${STAGE3}.DIGESTS.asc}"
+PORTAGE_URL="${PORTAGE_URL:-${MIRROR}snapshots/}"
+PORTAGE="${PORTAGE:-portage-${DATE}.tar.xz}"
+PORTAGE_SIG="${PORTAGE_SIG:-${PORTAGE}.gpgsig}"
+
+die()
+{
+       echo "$1"
+       exit 1
+}
+
+for FILE in "${STAGE3}" "${STAGE3_CONTENTS}" "${STAGE3_DIGESTS}"; do
+       if [ ! -f "downloads/${FILE}" ]; then
+               wget -O "downloads/${FILE}" "${ARCH_URL}${FILE}"
+               if [ "$?" -ne 0 ]; then
+                       rm -f "downloads/${FILE}" &&
+                       die "failed to download ${ARCH_URL}${FILE}"
+               fi
+       fi
+done
+
+for FILE in "${PORTAGE}" "${PORTAGE_SIG}"; do
+       if [ ! -f "downloads/${FILE}" ]; then
+               wget -O "downloads/${FILE}" "${PORTAGE_URL}${FILE}" ||
+               if [ "$?" -ne 0 ]; then
+                       rm -f "downloads/${FILE}" &&
+                       die "failed to download ${PORTAGE_URL}${FILE}"
+               fi
+       fi
+done
+
+sed -i "s/DATE=.*/DATE=\"\${DATE:-${DATE}}\"/" build.sh