Refactor 'check_pipeline_status' and add 'trigger_pipeline'

Rename 'check_pipeline_status' to 'mirror_pipeline_result' in order to better reflect what the function does.

Move determination of the pipeline out of this function to a new function 'get_pipelines' so that this can be tested separately and we can do different things depending on whether a pipeline exists or not.

Add function 'trigger_pipeline' to trigger a pipeline on a branch.

BCS 746-000635

get_pipelines.py

+#!/usr/bin/env python3
+import common
+
+import argparse
+import sys
+from gitlab import Gitlab
+from gitlab.v4.objects import Project
+
+
+def get_pipelines(project: Project, commit, ref: str):
+    """
+    Get all pipelines for a given commit and ref.
+    The ref can be negated with a preceding '^', e.g. '^master' finds pipelines on any
+    ref different from 'master'.
+    """
+
+    # Find pipelines for commit
+    pipelines = project.pipelines.list(sha=commit, retry_transient_errors=True)
+
+    # Remove pipelines not matching the ref condition
+    if ref:
+        for p in pipelines[:]:
+            if (
+                ref.startswith("^")
+                and p.ref == ref[1:]
+                or not ref.startswith("^")
+                and p.ref != ref
+            ):
+                pipelines.remove(p)
+
+    if not pipelines:
+        raise LookupError(
+            "No pipeline for commit '%s'%s found"
+            % (commit, " on ref '%s'" % ref if ref else "")
+        )
+
+    return pipelines
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--gitlab-url",
+        help="""URL to the GitLab instance""",
+        dest="gitlab_url",
+        required=True,
+    )
+    parser.add_argument(
+        "--token",
+        help="""GitLab REST API private access token""",
+        dest="token",
+        required=True,
+    )
+    parser.add_argument(
+        "--project",
+        help="""name of the GitLab project""",
+        dest="project",
+        required=True,
+    )
+    parser.add_argument(
+        "--commit",
+        help="""sha of the project commit to check""",
+        dest="commit",
+        required=True,
+    )
+    parser.add_argument(
+        "--ref",
+        help="""ref the pipeline ran on (can be negated with preceding '^')""",
+        dest="ref",
+        default="",
+        required=False,
+    )
+
+    args, _ = parser.parse_known_args()
+
+    gitlab = Gitlab(args.gitlab_url, private_token=args.token)
+    project = common.get_project(gitlab, args.project)
+
+    try:
+        pipelines = get_pipelines(project, args.commit, args.ref)
+    except LookupError as e:
+        sys.exit(e)
+
+    for p in pipelines:
+        print(p.id)
+
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    main()