[Issue #446] Fixes script to generate release notes

[widal001]

Summary

Fixes how the validate-and-generate-release-notes.sh handles the option --previous-tag "" which was breaking the CD workflows that were triggered without providing a previous tag.

• Fixes [Infra] Fix generate release notes script #446
• Time to review: 2 minutes

Changes proposed

What was added, updated, or removed in this PR.

• Fixes validate-and-generate-release-notes.sh to skip over the --previous-tag option when passed an empty string ""
• Improves code comments related to that parsing option

Context for reviewers

Testing instructions, background context, more in-depth details of the implementation, and anything else you'd like to call out or ask reviewers. Explain how the changes were verified.

The script failed if it received --previous-tag "" as an option because the script only ignored the previous tag if it was omitted or received no argument. This updates the option parsing to also skip parsing the previous tag option when set to an empty string ""

Additional information

Screenshots, GIF demos, code examples or output to help show the changes working as expected.

Testing locally

1. Recreate the issue on main by running this from the root of the repo. It should fail with Unknown option:

   .github/scripts/validate-and-generate-release-notes.sh \
      --prefix "@common-grants/cli@" \
      --config-file ".github/release-config/lib-cli.yml" \
      --release-tag "@common-grants/cli@0.2.4" \
      --previous-tag "" \
      --repository "HHS/simpler-grants-protocol" \
      --dry-run
   

2. Checkout this PR branch and re-run the script, and it should pass with:

    ✓ Latest tag '@common-grants/cli@0.2.4' is valid
    Generating release notes for @common-grants/cli@0.2.4
    
    === DRY RUN MODE - Release notes preview ===
    Latest tag: @common-grants/cli@0.2.4
    Previous tag: 
    
    <!-- Release notes generated using configuration in .github/release-config/lib-cli.yml at @common-grants/cli@0.2.4 -->
    
    
    
    **Full Changelog**: https://github.com/HHS/simpler-grants-protocol/compare/common-grants-sdk@0.4.0...@common-grants/cli@0.2.4
    === End of preview ===
   

Testing with GitHub action

Here's a dry run with the CLI workflow.

And here's another test with the Py SDK workflow: