shared git clone (#254)

* shared git clone

* unit tests

* contributors

* Update nightly_testing/generate_test_suite_cron.py

Co-authored-by: Yaswant Pradhan <2984440+yaswant@users.noreply.github.com>

* Update nightly_testing/tests/test_generate_test_suite_cron.py

Co-authored-by: Yaswant Pradhan <2984440+yaswant@users.noreply.github.com>

---------

Co-authored-by: Yaswant Pradhan <2984440+yaswant@users.noreply.github.com>

Author: james-bruten-mo

CONTRIBUTORS.md

@@ -1,6 +1,7 @@
 # Contributors
 
-| GitHub user | Real Name       | Affiliation | Date       |
-| ----------- | --------------- | ----------- | ---------- |
-| yaswant     | Yaswant Pradhan | Met Office  | 2026-07-17 |
-| jfrost-mo   | James Frost     | Met Office  | 2026-09-04 |
+| GitHub user       | Real Name       | Affiliation | Date       |
+| ----------------- | --------------- | ----------- | ---------- |
+| yaswant           | Yaswant Pradhan | Met Office  | 2026-07-17 |
+| jfrost-mo         | James Frost     | Met Office  | 2026-09-04 |
+| james-bruten-mo   | James Bruten    | Met Office  | 2026-09-10 |

nightly_testing/generate_test_suite_cron.py

@@ -82,7 +82,7 @@ def create_git_clone_cron(repo):
     length = len(command)
     command = f"{length * '#'}\n{command}\n{length * '#'}\n30 23 * * * "
     command += f"rm -rf {clone_path} ; "
-    command += f"git clone {repo_mirror} {clone_path}"
+    command += f"GIT_TRACE=1 GIT_TRACE_PERFORMANCE=1 git clone --shared {repo_mirror} {clone_path}"
     return command + "\n\n\n"
 
 

nightly_testing/tests/test_generate_test_suite_cron.py

@@ -83,7 +83,7 @@ def test_create_git_clone_cron():
         "###################################\n"
         "# Clone repo - every day at 23:30 #\n"
         "###################################\n"
-        f"30 23 * * * rm -rf {CLONE_DIR}/clone_repo ; git clone {MIRROR_PATH}MetOffice/repo.git {CLONE_DIR}/clone_repo\n\n\n"
+        f"30 23 * * * rm -rf {CLONE_DIR}/clone_repo ; GIT_TRACE=1 GIT_TRACE_PERFORMANCE=1 git clone --shared {MIRROR_PATH}MetOffice/repo.git {CLONE_DIR}/clone_repo\n\n\n"
     )
     assert create_git_clone_cron("repo") == expected