Fail fast on AppVeyor for repeated commits to same PR

Use AppVeyor's API!

reuse cached version of jq instead of downloading every time

make slightly more robust to network problems

appveyor.yml

@@ -32,6 +32,7 @@ cache:
  - llvm-3.3-i686-w64-mingw32-juliadeps.7z
  - llvm-3.3-x86_64-w64-mingw32-juliadeps.7z
  - make-3.81-2-msys-1.0.11-bin.tar.lzma
+ - jq.exe
 
 build_script:
 # Remove C:\MinGW\bin from the path, the version of MinGW installed on

contrib/windows/msys_build.sh

@@ -9,6 +9,22 @@ cd `dirname "$0"`/../..
 # Stop on error
 set -e
 
+# Fail fast on AppVeyor if there are newer pending commits in this PR
+curlflags="curl --retry 10 -k -L -y 5"
+if [ -n "$APPVEYOR_PULL_REQUEST_NUMBER" ]; then
+ # download a handy cli json parser
+ if ! [ -e jq.exe ]; then
+ $curlflags -O http:https://stedolan.github.io/jq/download/win64/jq.exe
+ fi
+ av_api_url="https://ci.appveyor.com/api/projects/StefanKarpinski/julia/history?recordsNumber=50"
+ query=".builds | map(select(.pullRequestId == \"$APPVEYOR_PULL_REQUEST_NUMBER\"))[0].buildNumber"
+ latestbuild="$(curl $av_api_url | ./jq "$query")"
+ if [ -n "$latestbuild" -a "$latestbuild" != "null" -a "$latestbuild" != "$APPVEYOR_BUILD_NUMBER" ]; then
+ echo "There are newer queued builds for this pull request, failing early."
+ exit 1
+ fi
+fi
+
 # If ARCH environment variable not set, choose based on uname -m
 if [ -z "$ARCH" -a -z "$XC_HOST" ]; then
  export ARCH=`uname -m`
@@ -61,8 +77,6 @@ case $(uname) in
  ;;
 esac
 
-curlflags="curl --retry 10 -k -L -y 5"
-
 # Download most recent Julia binary for dependencies
 if ! [ -e julia-installer.exe ]; then
  f=julia-latest-win$bits.exe