TAP is described here: https://testanything.org/

One new script, tapdiffer, does most of the heavy lifting.  It gets
rid of a lot of the hair in the test/Makefile pattern rules.  Other
sceits including singletest, singlelift, and liftcheck are also
up-gunned to emit TAP reports.  However, as of this commit,
nothing yet emits TAP plan lines.

Various test scripts have been heaily refactored while becoming TAP
producers; many are simplified using new procedures defined in
test/common-setup.sh. However, no test *logic* has changed; this
is just a re-skinning.

No TAP consumers have been assumed or defined.  Yet...

No Go code or anything else outside test/ is touched in this commit.