Make check:markdown successful for github domain checks

[MikeMcC399]

This PR resolves issue #664 "markdown-link-check produces wrong results and exit status"

1. To resolve the issue that link checking on the domain github.com results in 403 Forbidden errors, the new markdown-link-check configuration file md-linkcheck.json is added and it is referred to by the script check:markdown. After adding this config file, checks on links to github.com no longer produce a 403 error.

2. To resolve the issue that the action main.yml is successful, even when the markdown link check fails, the check:markdown script is converted to use xargs instead of exec as suggested in https://github.com/tcort/markdown-link-check#check-links-from-a-local-markdown-folder-recursive.

The new check:markdown script, which is invoked by npm run check:markdown is now defined as:

find *.md -print0 | xargs -0 -n1 markdown-link-check -c md-linkcheck.json

Changing the script ensures that no 403 (forbidden) errors are produced for otherwise correctly working links on github.com. Also if there are genuine link errors found, then the main.yml action will show failure, which should alert to one or more links which need correcting. In the past, link check failures went (apparently) unnoticed.

Verification

Verification with bad links

When there are known bad links in *.md files e.g. when npm run check:markdown finds 400 or 404 errors for links on the branch to be tested.

After main.yml has completed its run, examine the logs.

"Test on Node v14" has a red X. "Run npm run check:markdown" shows no 403 errors and completes with the message "Error: Process completed with exit code 123."

Verification with no bad links

When there are no known bad links in *.md files e.g. when npm run check:markdown finds no 400 or 404 errors for links on the branch to be tested.

After main.yml has completed its run, examine the logs of main.yml.

Look for success (green tick).

Matrix build-and-test shows 3 jobs completed.

Look at details of any of Test on Node v14 / v16 / v18. Drill down into "Run npm run check:markdown" which should end with no errors and a line similar to "134 links checked."

[MikeMcC399]

run 3688072982 was successful

There were no link check errors recorded. No more 403 errors (forbidden). The 400 and 404 errors were already removed by PR #665

This PR is now ready for review and merge.

[github-actions]

🎉 This PR is included in version 5.0.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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