- to avoid dupes.
- missing slashes.
- drop `.git` suffix from GitHub git repo URLs for a few outliers.
- use short YouTube URL like curl-www does.
- sync two RFC doc URLs with others.
Closes#19879
In an attempt to make them easier to find.
The man pages runtests.md and testcurl.md are in /docs
The rest of the test documentation is in /docs/tests
Closes#17463