ci: add generate_matrix script for CI

Problem: a script is needed to generate the GitHub CI matrix.

Add a script, copying it over from flux-core with modifications.

Author: jameshcorbett

src/test/generate_matrix.py

@@ -0,0 +1,163 @@
+#!/usr/bin/env python3
+#
+#  Generate a build matrix for use with github workflows
+#
+
+from copy import deepcopy
+import json
+import os
+import re
+import pathlib
+
+docker_run_checks = pathlib.Path("src/test/docker/docker-run-checks.sh")
+
+default_args = ""
+
+DOCKER_REPO = "libscr/scr"
+
+
+def on_master_or_tag(matrix):
+    return matrix.branch == "master" or matrix.tag
+
+
+DEFAULT_MULTIARCH_PLATFORMS = {
+    "linux/arm64": {
+        "when": lambda _: True,
+        "suffix": " - arm64",
+        "timeout_minutes": 90,
+        "runner": "ubuntu-24.04-arm",
+    },
+    "linux/amd64": {"when": lambda _: True, "suffix": " - amd64", "runner": "ubuntu-latest"},
+}
+
+
+class BuildMatrix:
+    def __init__(self):
+        self.matrix = []
+        self.branch = None
+        self.tag = None
+
+        #  Set self.branch or self.tag based on GITHUB_REF
+        if "GITHUB_REF" in os.environ:
+            self.ref = os.environ["GITHUB_REF"]
+            match = re.search("^refs/heads/(.*)", self.ref)
+            if match:
+                self.branch = match.group(1)
+            match = re.search("^refs/tags/(.*)", self.ref)
+            if match:
+                self.tag = match.group(1)
+
+    def create_docker_tag(self, image, env, command, platform):
+        """Create docker tag string if this is master branch or a tag"""
+        if self.branch == "master" or self.tag:
+            tag = f"{DOCKER_REPO}:{image}"
+            if self.tag:
+                tag += f"-{self.tag}"
+            if platform is not None:
+                tag += "-" + platform.split("/")[1]
+            env["DOCKER_TAG"] = tag
+            command += f" --tag={tag}"
+            return True, command
+
+        return False, command
+
+    def add_build(
+        self,
+        name=None,
+        image=None,
+        args=default_args,
+        jobs=6,
+        env=None,
+        docker_tag=False,
+        platform=None,
+        command_args="",
+        timeout_minutes=60,
+        runner="ubuntu-latest",
+    ):
+        """Add a build to the matrix.include array"""
+
+        # Extra environment to add to this command:
+        # NOTE: ensure we copy the dict rather than modify, re-used dicts can cause
+        #       overwriting
+        env = dict(env) if env is not None else {}
+
+        needs_buildx = False
+        if platform:
+            command_args += f"--platform={platform}"
+            needs_buildx = True
+
+        # The command to run:
+        command = f"{docker_run_checks} -j{jobs} --image={image} {command_args}"
+
+        if docker_tag:
+            #  Only export docker_tag if this is main branch or a tag:
+            docker_tag, command = self.create_docker_tag(image, env, command, platform)
+
+        create_release = False
+        if self.tag and "DISTCHECK" in env:
+            create_release = True
+
+        command += f" -- {args}"
+
+        self.matrix.append(
+            {
+                "name": name,
+                "env": env,
+                "command": command,
+                "image": image,
+                "runner": runner,
+                "tag": self.tag,
+                "branch": self.branch,
+                "docker_tag": docker_tag,
+                "needs_buildx": needs_buildx,
+                "create_release": create_release,
+                "timeout_minutes": timeout_minutes,
+            }
+        )
+
+    def add_multiarch_build(
+        self,
+        name: str,
+        platforms=DEFAULT_MULTIARCH_PLATFORMS,
+        default_suffix="",
+        image=None,
+        docker_tag=True,
+        **kwargs,
+    ):
+        for p, args in platforms.items():
+            if args["when"](self):
+                suffix = args.get("suffix", default_suffix)
+                self.add_build(
+                    name + suffix,
+                    platform=p,
+                    docker_tag=docker_tag,
+                    image=image if image is not None else name,
+                    command_args=args.get("command_args", ""),
+                    timeout_minutes=args.get("timeout_minutes", 30),
+                    runner=args["runner"],
+                    **kwargs,
+                )
+
+    def __str__(self):
+        """Return compact JSON representation of matrix"""
+        return json.dumps(
+            {"include": self.matrix}, skipkeys=True, separators=(",", ":")
+        )
+
+
+matrix = BuildMatrix()
+
+
+for name in ("bookworm", "alpine", "fedora40"):
+    matrix.add_multiarch_build(name=name)
+
+matrix.add_build(
+    name="el9 - arm64",
+    image="el9",
+    platform="linux/arm64",
+    runner="ubuntu-24.04-arm",
+    docker_tag=True
+)
+
+
+print(matrix)