strcmp falsely claims it returns a 0, 1 or -1

[ash-m]

The docs for strcmp say:

Return Values ¶

Returns -1 if string1 is less than string2; 1 if string1 is greater than string2, and 0 if they are equal.

Changelog ¶

Version	Description
8.2.0	This function now returns -1 or 1, where it previously returned a negative or positive integer.

Problems:

• The "Return Values" part is patentenly not true: https://3v4l.org/CXhkE#v8.2.0
• I believe the "Changelog" is refering to when a string is compared to an empty string: https://3v4l.org/UHXcr

I believe the intended logic here is:

• Attempt to calculate the spread between to strings (unpredictable for large spreads)
• If the strings match except for trailing characters, return the difference in characters

Whatever the logic, it seems like it does not return very predicable results other than being contrasted to 0. Here are some interesting return values: https://3v4l.org/FN86s

[cmb69]

See #3223. While this has been fixed in the migration guide (but not in UPGRADING), the fix apparently missed the changelog entries.