1 files changed, 40 insertions, 0 deletions
diff --git a/ops/pipelines/fetch-parent-targets.sh b/ops/pipelines/fetch-parent-targets.sh
new file mode 100755
index 000000000000..bc334fc35cb1
--- /dev/null
+++ b/ops/pipelines/fetch-parent-targets.sh
@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+set -ueo pipefail
+
+# Each Buildkite build stores the derivation target map as a pipeline
+# artifact. This script determines the most appropriate commit (the
+# fork point of the current chain from canon) and fetches the
+# artifact.
+#
+# Since builds can be based on canon before the pipeline for the last
+# commit has finished, it is possible that the fork point has no
+# target map. To account for this, we will go up to 3 commits back in
+# time to find a map.
+#
+# If no map is found, the failure mode is not critical: We simply
+# build all targets.
+
+function most_relevant_builds {
+    git fetch -v origin canon
+    local FIRST=$(git merge-base --fork-point HEAD origin/canon)
+    local SECOND=$(git rev-parse "$FIRST~1")
+    local THIRD=$(git rev-parse "$FIRST~2")
+
+    curl 'https://graphql.buildkite.com/v1' \
+         --silent \
+         -H "Authorization: Bearer $(cat /run/agenix/buildkite-graphql-token)" \
+         -d "{\"query\": \"query { pipeline(slug: \\\"tvl/depot\\\") { builds(commit: [\\\"$FIRST\\\",\\\"$SECOND\\\",\\\"$THIRD\\\"]) { edges { node { uuid }}}}}\"}" | \
+         jq -r '.data.pipeline.builds.edges[] | .node.uuid'
+}
+
+mkdir -p tmp
+for build in $(most_relevant_builds); do
+    echo "Checking artifacts for build $build"
+    buildkite-agent artifact download --build "${build}" 'pipeline/drvmap.json' 'tmp/' || true
+
+    if [[ -f "tmp/pipeline/drvmap.json" ]]; then
+        echo "Fetched target map from build ${build}"
+        mv tmp/pipeline/drvmap.json parent-target-map.json
+        break
+    fi
+done