Skip snap build for PRs if nothing under snap/ is modified

Additionally relegate push snap build to a secondary CI pipeline

ci/buildkite-snap.yml

@@ -0,0 +1,4 @@
+steps:
+  - command: "ci/snap.sh"
+    timeout_in_minutes: 30
+    name: "snap [public]"

ci/buildkite.yml

@@ -18,14 +18,16 @@ steps:
         limit: 2
     agents:
       - "queue=cuda"
-  - command: "ci/snap.sh [public]"
+  - command: "ci/pr-snap.sh"
     timeout_in_minutes: 30
     name: "snap [public]"
   - wait
-  - command: "ci/publish-crate.sh [public]"
+  - command: "ci/publish-crate.sh"
     timeout_in_minutes: 20
-    name: "publish crate"
+    name: "publish crate [public]"
-  - command: "ci/hoover.sh [public]"
+  - command: "ci/hoover.sh"
     timeout_in_minutes: 20
-    name: "clean agent"
+    name: "clean agent [public]"
-
+  - trigger: "solana-snap"
+    branches: "master"
+    async: true

ci/is-pr.sh

@@ -0,0 +1,8 @@
+#!/bin/bash -e
+#
+# The standard BUILDKITE_PULL_REQUEST environment variable is always "false" due
+# to how solana-ci-gate is used to trigger PR builds rather than using the
+# standard Buildkite PR trigger.
+#
+
+[[ $BUILDKITE_BRANCH =~ pull/* ]]

ci/pr-snap.sh

@@ -0,0 +1,18 @@
+#!/bin/bash -e
+#
+# Only run snap.sh for pull requests that modify files under /snap
+#
+
+cd "$(dirname "$0")"
+
+if ./is-pr.sh; then
+  affected_files="$(buildkite-agent meta-data get affected_files)"
+  echo "Affected files in this PR: $affected_files"
+  if [[ ! ":$affected_files:" =~ :snap/ ]]; then
+    echo "Skipping snap build as no files under /snap were modified"
+    exit 0
+  fi
+  exec ./snap.sh
+else
+  echo "Skipping snap build as this is not a pull request"
+fi

ci/snap.sh

@@ -3,7 +3,7 @@
 cd "$(dirname "$0")/.."
 
 DRYRUN=
-if [[ -z $BUILDKITE_BRANCH || $BUILDKITE_BRANCH =~ pull/* ]]; then
+if [[ -z $BUILDKITE_BRANCH ]] || ./ci/is-pr.sh; then
   DRYRUN="echo"
 fi