yes: remove cfg & move ownership of buffer to fn exec

[oech3]

buffer is never used after fn exec. So move ownership.
Required for #11458 to extract len() before growing it.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/tail/retry is no longer failing!
Congrats! The gnu test tests/timeout/timeout-group is no longer failing!
Note: The gnu test tests/cp/link-heap is now being skipped but was previously passing.
Note: The gnu test tests/dd/no-allocate is now being skipped but was previously passing.

[RenjiSann]

Sorry I thought you wanted to merge #11458 before

[oech3]

No problem. Easy to rebase.

[oech3]

prepare_buffer is not a good name for me. How about renaming it to grow_buffer to clarify that buffer is modified?

[xtqqczze]

prepare_buffer is not a good name for me. How about renaming it to grow_buffer to clarify that buffer is modified?

"grow" doesn't suggest to me the buffer is written, how about repeat_from_within?

[oech3]

How about let buffer = repeated_buffer(buffer) for shorter name? I don't see any reason to avoid moving ownership again.

[RenjiSann]

Let's make it clear before we make it short.
I'd go with repeat_content_to_capacity, wdyt ?

[oech3]

It sometimes does not exactly fit to capacity. But OK.

[RenjiSann]

It sometimes does not exactly fit to capacity. But OK.

Yes, and that's a detail you get upon read the docstring, which is fine.
Let's not be too verbose either 😁