Add comments explaining different hashFiles() argument

The other cache keys for our GHA jobs are in the format '**/<filename>' so that
any file with that name is used in the repository. However, for Python packages
they may have a 'setup.py' as part of their internal codebase that does not
impact environment requirements. As a result we only want to use the 'setup.py'
that is in the root of the repository and is used to install the package.

Co-authored-by: dav3r <david.redmin@trio.dhs.gov>

.github/workflows/build.yml

@@ -28,6 +28,9 @@ jobs:
           path: |
             ${{ env.PIP_CACHE_DIR }}
             ${{ env.PRE_COMMIT_CACHE_DIR }}
+          # We do not use '**/setup.py' in the cache key so only the 'setup.py'
+          # file in the root of the repository is used. This is in case a Python
+          # package were to have a 'setup.py' as part of its internal codebase.
           key: "${{ env.BASE_CACHE_KEY }}\
             ${{ hashFiles('**/requirements-test.txt') }}-\
             ${{ hashFiles('**/requirements.txt') }}-\
@@ -60,6 +63,9 @@ jobs:
             py${{ steps.setup-python.outputs.python-version }}-"
         with:
           path: ${{ env.PIP_CACHE_DIR }}
+          # We do not use '**/setup.py' in the cache key so only the 'setup.py'
+          # file in the root of the repository is used. This is in case a Python
+          # package were to have a 'setup.py' as part of its internal codebase.
           key: "${{ env.BASE_CACHE_KEY }}\
             ${{ hashFiles('**/requirements-test.txt') }}-\
             ${{ hashFiles('**/requirements.txt') }}-\
@@ -97,6 +103,9 @@ jobs:
             py${{ steps.setup-python.outputs.python-version }}-"
         with:
           path: ${{ env.PIP_CACHE_DIR }}
+          # We do not use '**/setup.py' in the cache key so only the 'setup.py'
+          # file in the root of the repository is used. This is in case a Python
+          # package were to have a 'setup.py' as part of its internal codebase.
           key: "${{ env.BASE_CACHE_KEY }}\
             ${{ hashFiles('**/requirements-test.txt') }}-\
             ${{ hashFiles('**/requirements.txt') }}-\
@@ -129,6 +138,9 @@ jobs:
             py${{ steps.setup-python.outputs.python-version }}-"
         with:
           path: ${{ env.PIP_CACHE_DIR }}
+          # We do not use '**/setup.py' in the cache key so only the 'setup.py'
+          # file in the root of the repository is used. This is in case a Python
+          # package were to have a 'setup.py' as part of its internal codebase.
           key: "${{ env.BASE_CACHE_KEY }}\
             ${{ hashFiles('**/requirements.txt') }}-\
             ${{ hashFiles('setup.py') }}"