#171: Allow cubelist with only one history to be saved

[Theo Geddes (mo-tgeddes)]

Closes #171

To be completed prior to review request and updated as required during the review process.

If the answer to an item on the list is not applicable, feel free to replace the checkbox with 'N/A' to give extra clarity.

All developers are reminded to follow the ancil working practices

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Branch

Related branches (e.g. ancillary-file-science):

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ANTS rose stem logs

dev-ants-core/run132

ancillary-file-science rose stem logs

n/a

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Testing

For core ANTS only tests, the bare minimum that will be accepted is the group=unittests but many, if not most, changes will need to test other groups to ensure they meet reviewer expectations. In general, it should be possible and is advised to run the group=all group prior to review submission as this will catch any consequential issues. Additionally you must run the ancillary-file-science tests, pointing at your branch, with group=all to capture any behaviour changes affecting Science codes.

If your change will alter existing science results, you will need to seek appropriate Scientific validation and confirm that the model has been initialised with your new development. Inspecting a change in xconv/pyplot/visualiser of choice is not sufficient to demonstrate the model can be initialised from your file.

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Impact of change

• This will maintain results for ANTS cylc vip ./rose-stem -z group=all tests
• This will this maintain results for ancillary-file-science cylc vip ./rose-stem -z group=all tests
• If this change adds a new capability, evidence has been supplied to show testing of ancillary generation across different resolutions e.g. For global ancillary generation capabilities for use in NWP n1280e is expected to have been tested
• This change has significantly impacted required resources (runtime and memory) in existing ancillary generation (if yes, give details)
• This change alters existing ancils

Add further comments/details for your reviewers here on the impacts of the change......

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Approvals for this change

• I have approval from the ANTS core development team for these changes

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New functionality further testing

• If adding new functionality to existing codes, I confirm that the new code doesn't change results when it is switched off and ''works'' when switched on
• Unittests have been added
• Rose stem tests have been added for any new functionality
• If adding new functionality please confirm that the new code compares across different standard decompositions.
• I have not encountered any failures in my rose-stem output(s)
  These tasks must succeed for your ticket to pass review.
• I have remembered to run the code style check tasks/tools

Add details of any further testing here.

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Other

• I have read the Contributor Licence Agreement
• I have added my name and affiliation to the Contributors list if I am not already on there in this PR.
• The issue labels, milestones, etc. are correct
• Links to all related issues have been provided in the pull request description
• I have requested a code reviewer
• Source data has been added or changed - please include a link to the license

I confirm that all code is my own and that my contributions are not subject to copyright or license restrictions (see Contributor Licence Agreement).	Theo Geddes
I confirm I have not knowingly violated intellectual property rights (IPR) and have taken sensible measures to prevent doing so, including appropriate attribution for usage of Generative AI. I confirm that this work is my own, and I understand that it is my responsibility to ensure I am not violating others’ IPR. This includes taking reasonable steps to ensure that all tools used while creating this contribution did not infringe IPR.	Theo Geddes

Please add any further notes here. If Generative AI tools have been used, a brief summary (e.g. "Github copilot used to add extra unittests") should be provided.

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Rose stem logs

Please copy in the contents of your trac_status.log file(s) below (found in the cylc-run directory for your rose stem run) to your rose-stem testing here. Note: if your changes lead to a change in answers, you must run cylc vip ./rose-stem -z group=all to help ensure all affected configurations has been flagged up.

Tue 25 Aug 15:40:13 BST 2026 Git status: [ "?? ../ants.tests", "?? ../history-test.nc", "?? ../import-test.py", "?? ../mpi-fix.lock", "?? ../new-env.lock", "?? ../wildcard1.pp", "?? ../wildcard1.pp.license", "?? ../wildcard2.pp" ] Commit: 5b63333

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Test Results - Summary

tasks	total
succeeded	65

Test Results - Detail

task	status
install_cold	succeeded
ancil_general_regrid_grid_to_grid_spiral_split2	succeeded
black	succeeded
ancil_2anc_split0	succeeded
ancil_general_regrid_grid_to_variable_resolution_grid_split2	succeeded
ancil_general_regrid_grid_to_n48e_namelist_split2	succeeded
ancil_general_regrid_grid_to_grid_kdtree_split1	succeeded
ancil_general_regrid_3d_to_3d_split2	succeeded
build_docs	succeeded
ancil_general_regrid_grid_to_grid_kdtree_split0	succeeded
ancil_general_regrid_grid_to_n48_namelist_split1	succeeded
ancil_general_regrid_grid_to_n48_namelist_split2	succeeded
ancil_create_ite_shapefile	succeeded
ancil_general_regrid_3d_to_3d_split0	succeeded
ancil_general_regrid_grid_to_n48e_namelist_split0	succeeded
ancil_general_regrid_invert_mask_kdtree_split1	succeeded
ancil_general_regrid_invert_mask_kdtree_split0	succeeded
ancil_general_regrid_3d_to_3d_split1	succeeded
ancil_general_regrid_with_time_constraint_latitude_weighted_kdtree_split2	succeeded
ancil_fill_n_merge_invert_mask_spiral	succeeded
ancil_fill_n_merge_invert_mask_latitude_weighted_kdtree	succeeded
ancil_general_regrid_with_time_constraint_latitude_weighted_kdtree_split0	succeeded
unittests	succeeded
ancil_general_regrid_3d_to_3d_with_extrapolation_split0	succeeded
ancil_general_regrid_with_time_constraint_spiral_split2	succeeded
ancil_general_regrid_invert_mask_spiral_split1	succeeded
ancil_general_regrid_with_time_constraint_kdtree_split1	succeeded
ancil_general_regrid_invert_mask_latitude_weighted_kdtree_split0	succeeded
ancil_general_regrid_grid_to_grid_spiral_split1	succeeded
ancil_general_regrid_3d_to_3d_with_extrapolation_split2	succeeded
ancil_general_regrid_grid_to_n48e_namelist_split1	succeeded
ancil_general_regrid_invert_mask_latitude_weighted_kdtree_split1	succeeded
ancil_general_regrid_with_time_constraint_kdtree_split2	succeeded
ancil_general_regrid_with_time_constraint_spiral_split0	succeeded
ancil_general_regrid_with_time_constraint_kdtree_split0	succeeded
ancil_general_regrid_with_time_constraint_spiral_split1	succeeded
ancil_2anc_split2	succeeded
ancil_general_regrid_grid_to_grid_spiral_split0	succeeded
ancil_general_regrid_invert_mask_spiral_split2	succeeded
ancil_general_regrid_invert_mask_spiral_split0	succeeded
ancil_general_regrid_grid_to_grid_latitude_weighted_kdtree_split2	succeeded
ancil_general_regrid_with_time_constraint_latitude_weighted_kdtree_split1	succeeded
ancil_general_regrid_invert_mask_kdtree_split2	succeeded
flake8	succeeded
ancil_general_regrid_grid_to_variable_resolution_grid_split1	succeeded
ancil_general_regrid_grid_to_variable_resolution_grid_split0	succeeded
ancil_general_regrid_invert_mask_latitude_weighted_kdtree_split2	succeeded
ancil_2anc_split1	succeeded
ancil_general_regrid_grid_to_grid_latitude_weighted_kdtree_split1	succeeded
ancil_general_regrid_grid_to_n48_namelist_split0	succeeded
ancil_general_regrid_grid_to_grid_latitude_weighted_kdtree_split0	succeeded
isort	succeeded
ancil_general_regrid_grid_to_grid_kdtree_split2	succeeded
ancil_fill_n_merge_invert_mask_kdtree	succeeded
ancil_general_regrid_3d_to_3d_with_extrapolation_split1	succeeded
ancil_fill_n_merge_land_cover_kdtree	succeeded
ancil_fill_n_merge_land_cover_spiral	succeeded
ancil_fill_n_merge_land_cover_latitude_weighted_kdtree	succeeded
rose_ana_2anc	succeeded
rose_ana_fill_n_merge	succeeded
rose_ana_general_regrid_kdtree	succeeded
rose_ana_general_regrid	succeeded
rose_ana_general_regrid_spiral	succeeded
rose_ana_general_regrid_latitude_weighted_kdtree	succeeded
linkcheck	succeeded

[Jenny Hickson (jennyhickson)]

Looks good to me - this now echos the similar code in cube.py.