[BUG?] "git config --replace-all key value value_regex" ignores value_regex?

[Derrick Stolee <stolee@gmail.com>]

As discussed [1], I am working on relaxing the "regex" part of the
value_regex parameter in the "git config" command.

[1] https://lore.kernel.org/git/xmqqlfez6alb.fsf@gitster.c.googlers.com/

As I am working to solidify how this command works, I'm adding tests
for all of the compatible options that could use a "--literal-value"
modifier. One that seemed helpful to use was "--replace-all". The
docs have this line in the SYNOPSIS:

'git config' [<file-option>] [--type=<type>] [--literal-value] --replace-all name value [value_regex]

and this in the OPTIONS:

--replace-all::
	Default behavior is to replace at most one line. This replaces
	all lines matching the key (and optionally the value_regex).

However, this test fails:

test_expect_success '--replace-all and value_regex' '
	q_to_tab >.git/config <<-\EOF &&
	[abc]
	Qkey = one
	Qkey = two
	Qkey = three
	EOF
	q_to_tab >expect <<-\EOF &&
	[abc]
	Qkey = four
	Qkey = two
	Qkey = three
	EOF
	git config --replace-all abc.key four "o*" &&
	test_cmp expect .git/config
'

The end result is that _all_ existing values are removed in
favor of one final result of abc.key=four.

Is this the intended behavior? It seems like value_regex is completely
ignored instead of actually performing a function here. The only
mailing list reference I can find include a doc update [2] and the original
implementation from 2005 [3].

[2] https://lore.kernel.org/git/alpine.LFD.2.21.1805300733440.10096@localhost.localdomain/
[3] https://lore.kernel.org/git/Pine.LNX.4.63.0511200650130.12832@wbgn013.biozentrum.uni-wuerzburg.de/

If it is _not_ the intended behavior, then would a fix to make my test
pass be appropriate? If anyone is currently specifying a value_regex
to this command, then the behavior would change in surprising ways.
However, it seems that they would get the same behavior without using
value_regex.

Thanks,
-Stolee