modification time plugin does not handle symlinked parent/grandparent directories

```
[GTN/Time/Mod] No git cached time available for topics/microbiome/tutorials/mothur-miseq-sop-short/faqs/index.md, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/data-science/tutorials/data-manipulation-olympics/workflows/data_manipulation_olympics_with_exercises.ga, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/data-science/tutorials/data-manipulation-olympics/workflows/index.md, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/contributing/tutorials/fair-gtn/faqs/index.md, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/fair/tutorials/med-chem-data/faqs/index.md, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/fair/tutorials/med-chem-data/workflows/Data-management-in-Medicinal-Chemistry-workflow.ga, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/fair/tutorials/med-chem-data/workflows/index.md, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/assembly/tutorials/metagenomics-assembly/workflows/metagenomics_assembly_tutorial_workflow.ga, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/assembly/tutorials/metagenomics-assembly/workflows/workflow-generate-dataset-for-assembly-tutorial.ga, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/assembly/tutorials/metagenomics-assembly/workflows/index.md, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/microbiome/tutorials/mothur-miseq-sop-short/faqs/input_not_found.md, defaulting to checkout
[GTN/Time/Mod] No git cached time available for topics/microbiome/tutorials/mothur-miseq-sop-short/faqs/more_info.md, defaulting to checkout
```