From c168cee1054fa6a5a993d5033950f6803bc29569 Mon Sep 17 00:00:00 2001
From: Alec Warner <antarus@gentoo.org>
Date: Mon, 19 Mar 2018 19:58:57 -0400
Subject: Avoid manual intervention when we miss a snapshot.

If yesterday's snapshot is missing, scan for the last successful
snapshot.
---
 snapshots-create.sh | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/snapshots-create.sh b/snapshots-create.sh
index f6af8ac..f29dec6 100755
--- a/snapshots-create.sh
+++ b/snapshots-create.sh
@@ -44,8 +44,21 @@ if [[ ! $(gpg --list-keys ${SIGNKEYID} | grep ${SIGNKEYID}) ]]; then
 	exit 1
 fi
 
-if [[ ! -e "${UPLOAD}/${DELTA_FILENAME}" ]]; then
-	echo "Previous snapshot does not exist: '${UPLOAD}/${DELTA_FILENAME}'"
+# Use yesterdays snapshot, if its unavailable, use the 'latest' snapshot.
+# If both are missing, bail out.
+POTENTIAL_SNAPSHOTS=(
+	${UPLOAD}/${DELTA_FILENAME}
+	${UPLOAD}/portage-latest.tar.bz2
+	FAIL
+)
+
+for previous_snapshot in ${POTENTIAL_SNAPSHOTS[*]}; do
+	[[ -e ${previous_snapshot} ]] && break
+done
+
+if [[ ${previous_snapshot} == FAIL ]]; then
+	# Cut FAIL out of the printed list, to ease debugging.
+	echo "Previous snapshots do not exist: ${POTENTIAL_SNAPSHOTS[*]:0:2}"
 	exit 1
 fi
 
@@ -138,19 +151,19 @@ write_time_log "END TARBALL		$(date -u)"
 # 2) Sanity check the tarball size and bail out if it appears abnormal.
 write_time_log "START SIZE SANITY	$(date -u)"
 current_size=$(stat -c '%s' "${FILENAME}")
-previous_size=$(stat -c '%s' "${UPLOAD}/${DELTA_FILENAME}")
+previous_size=$(stat -c '%s' "${previous_snapshot}")
 if [ ${current_size} -lt ${previous_size} ]; then
 	size_difference=$(expr ${previous_size} - ${current_size})
 	difference_ratio=$(expr ${previous_size} / ${size_difference})
 	if [ ${difference_ratio} -lt 2 ]; then
 		echo "Snapshot size has decreased by more than 50% in one day!!!"
 		echo "${FILENAME} ${current_size} bytes"
-		echo "${DELTA_FILENAME} ${previous_size} bytes"
+		echo "${previous_snapshot} ${previous_size} bytes"
 		exit 1
 	elif [ ${difference_ratio} -lt 5 ]; then
 		echo "Snapshot size has decreased by more than 20% in one day!!!"
 		echo "${FILENAME} ${current_size} bytes"
-		echo "${DELTA_FILENAME} ${previous_size} bytes"
+		echo "${previous_snapshot} ${previous_size} bytes"
 		# Make this non-fatal while we recover more space.
 		#exit 1
 	fi
@@ -192,7 +205,7 @@ write_time_log "END SIGN		$(date -u)"
 write_time_log "START DELTA		$(date -u)"
 PATCH=snapshot-${DELTA_BASE}-${YESTERDAY}.patch.bz2
 if [ ! -f "${PATCH}" ]; then
-	${NICE} ${BZIP2_PROG} -dkc ${UPLOAD}/${DELTA_FILENAME} > orig
+	${NICE} ${BZIP2_PROG} -dkc "${previous_snapshot}" > orig
 	/usr/bin/differ -f bdelta orig ${FILENAME%.bz2} ${PATCH%.bz2}
 	${NICE} ${BZIP2_PROG} -9 ${PATCH%.bz2}
 	md5sum ${PATCH} > ${PATCH}.md5sum
-- 
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