changed-files: ignore empty patterns

[dbarbuzzi]

Summary:

Update the changed-files action so that "empty" patterns are ignored (empty/only whitespace). Also, add some logging to help improve clarity.

Test Plan:

# run in a repo where there was one changed file that previously
# wasn't being picked up due to an "empty" exclude pattern
$ export INCLUDE_PATTERN=$(cat <<EOF
^src/
^tests/
^\.github/workflows/test-check-transformers\.yaml$
^MANIFEST\.in$
^setup\.py$
EOF
)
$ export EXCLUDE_PATTERN=$(cat <<EOF
^tests/e2e/
^tests/lmeval/
^tests/examples/
\.md$
EOF
)
$ bash check-files.sh 
CHANGED_FILES: .github/workflows/test-check-transformers.yaml
including: .github/workflows/test-check-transformers.yaml (pattern: ^\.github/workflows/test-check-transformers\.yaml$)
all_changed_files=.github/workflows/test-check-transformers.yaml

Related Issues:

n/a