From 50b69ad06bd4b4d757badd1b00f5f645abcc0ee8 Mon Sep 17 00:00:00 2001
From: Andrew Scheller <github@loowis.durge.org>
Date: Mon, 12 Dec 2016 20:46:27 +0000
Subject: [PATCH] chore: download files to a temporary filename first, then
 rename (#973)

This avoids the failure-mode where wget got interrupted (e.g. network error
or server timeout), which caused the download-tool.sh to stop, which caused
the current make to stop. However if you then ran make again, it would see
that the file existed (and not know that it was incomplete / corrupt) and so
not try downloading it again. This commit fixes the problem by modifying
download-tool.sh to download to a temporary filename, and only rename to the
final destination filename after the checksum has been verified.
---
 scripts/build/download-tool.sh | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/scripts/build/download-tool.sh b/scripts/build/download-tool.sh
index 15aaccf5..397e5c1e 100755
--- a/scripts/build/download-tool.sh
+++ b/scripts/build/download-tool.sh
@@ -63,7 +63,13 @@ function checksum_matches() {
 	test "$($SHA256SUM $file | cut -d ' ' -f1)" = "$hash"
 }
 
-if [ -e "$ARGV_OUTPUT" ]; then
+TEMP_OUTPUT="$ARGV_OUTPUT.TMP"
+
+if [ -f "$TEMP_OUTPUT" ]; then
+  rm "$TEMP_OUTPUT"
+fi
+
+if [ -f "$ARGV_OUTPUT" ]; then
   if checksum_matches "$ARGV_OUTPUT" "$ARGV_CHECKSUM"; then
     echo "Re-using from cache"
     exit 0
@@ -72,12 +78,14 @@ if [ -e "$ARGV_OUTPUT" ]; then
   fi
 fi
 
-wget --no-check-certificate "$ARGV_URL" -O "$ARGV_OUTPUT"
+wget --no-check-certificate "$ARGV_URL" -O "$TEMP_OUTPUT"
 
-if ! checksum_matches "$ARGV_OUTPUT" "$ARGV_CHECKSUM"; then
+if ! checksum_matches "$TEMP_OUTPUT" "$ARGV_CHECKSUM"; then
   echo "Checksum mismatch" 1>&2
-  rm -f "$ARGV_OUTPUT"
+  rm "$TEMP_OUTPUT"
   exit 1
+else
+  mv "$TEMP_OUTPUT" "$ARGV_OUTPUT"
 fi
 
 if [ "$ARGV_EXECUTE_PERMISSIONS" == "true" ]; then