Make CI only build/test modules with any changes

.github/bin/build-matrix-from-impacted.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+
+import argparse
+import yaml
+import json
+import logging
+import sys
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Filter test matrix modules using list of impacted modules."
+    )
+    parser.add_argument(
+        "-m",
+        "--matrix",
+        type=argparse.FileType("r"),
+        default=".github/test-matrix.yaml",
+        help="A YAML file with the test matrix",
+    )
+    parser.add_argument(
+        "-i",
+        "--impacted",
+        type=argparse.FileType("r"),
+        default="gib-impacted.log",
+        help="File containing list of impacted modules, one per line, "
+        "as paths, not artifact ids",
+    )
+    parser.add_argument(
+        "-o",
+        "--output",
+        type=argparse.FileType("w"),
+        default=sys.stdout,
+        help="Filename to write impacted modules matrix JSON to",
+    )
+    parser.add_argument(
+        "-v",
+        "--verbose",
+        action="store_const",
+        dest="loglevel",
+        const=logging.INFO,
+        default=logging.WARNING,
+        help="Print info level logs",
+    )
+
+    args = parser.parse_args()
+    logging.basicConfig(level=args.loglevel)
+    build(args.matrix, args.impacted, args.output)
+
+
+def build(matrix_file, impacted_file, output_file):
+    matrix = yaml.load(matrix_file, Loader=yaml.Loader)
+    impacted = list(filter(None, [line.strip() for line in impacted_file.readlines()]))
+    logging.info("Read matrix: %s", matrix)
+    logging.info("Read impacted: %s", impacted)
+    include = []
+    for item in matrix.get("include", []):
+        modules = item.get("modules", [])
+        if isinstance(modules, str):
+            modules = [modules]
+        if not any(module in impacted for module in modules):
+            logging.info("Excluding matrix section: %s", item)
+            continue
+        include.append(
+            {
+                # concatenate because matrix values should be primitives
+                "modules": ",".join(modules),
+                "profile": item.get("profile", ""),
+            }
+        )
+    if include:
+        matrix["include"] = include
+    json.dump(matrix, output_file)
+    output_file.write("\n")
+
+
+if __name__ == "__main__":
+    main()

.github/bin/git-fetch-base-ref.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+set -euo pipefail
+
+if [ -z "${GITHUB_BASE_REF:-}" ] || [ "$GITHUB_BASE_REF" == master ]; then
+    echo >&2 "GITHUB_BASE_REF is not set or is master, not fetching it"
+    exit 0
+fi
+
+git fetch --no-tags --prune origin "$GITHUB_BASE_REF"