bug#63398: 28.2; Doc or behavior of replacement commands (e.g. `replace-string')

[Juri Linkov]

>> You closed this as fixed, but I still find the doc
>> - or the behavior - unclear wrt this example.
>> Could you maybe (e.g. here) explain a bit more how
>> the behavior fits the description?
>
> I don't know what exactly happens and when, and thus cannot say more.
> Feel free to study the code and find out.  Or maybe someone else will
> be able to describe the behavior in more detail.

The rules of replacement case-folding are more complex than documented.
`replace-match' checks if the initial is a caseless word constituent
like "0", and treats that like a lowercase initial.

So  "test a → test b" replaces "Test A" with "Test B",
but "test 0 → test 1" replaces "Test 0" with "test 1".