find(1): Don't skip unreadable directories in -depth mode

[tavianator_tavianator.com]

Summary

find -depth skips unreadable directories, while find without -depth
prints them. For example:

$ mkdir -p foo/bar
$ chmod -r foo
$ find foo -depth 2>/dev/null
foo
$ find foo 2>/dev/null
foo
foo/bar

See https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=244561

Test Plan

Added a test to find_test.sh.

[pstef]

Added a test to find_test.sh. The test fails when run as root though.

See how usr.sbin/extattr/tests/extattr_test.sh or tests/sys/cddl/zfs/tests/cli_user/misc/misc_test.sh use the unprivileged user.

[pstef]

@tavianator_tavianator.com this worked for me, could you check?

atf_test_case find_depth_error
find_depth_error_head()
{
	atf_set "descr" "Verifies that unreadable directories are still " \
	    "reported in -depth mode"
	atf_set "require.user" "unprivileged"
}
find_depth_error_body()
{
	atf_check -s exit:0 mkdir -p test/dir
	atf_check -s exit:0 chmod -r test

	atf_check -s exit:1 -o "inline:test\n" -e ignore find test -depth
	atf_check -s exit:1 -o "inline:test\n" -e ignore find test
}

[tavianator_tavianator.com]

Make sure the test uses an unprivileged user

[pstef]

usr.bin/find/tests/find_test.sh

80–81

These seem to be copied from another test case.

82

With the way test/dir was setup above, I don't get that output. Here it's merely "test\n" on stdout.

[tavianator_tavianator.com]

Write the comment instead of copy-pasting it

[tavianator_tavianator.com]

usr.bin/find/tests/find_test.sh

82

Right but I did chmod -r test/dir and you did chmod -r test. I can change it to yours if you want.

[pstef]

usr.bin/find/tests/find_test.sh

82

I don't have a preference here, at least not yet. I did chmod -r test because the example both in the description of this differential and your comment in the PR do chmod -r foo and not chmod -r foo/bar. Maybe we could go for the most coverage, testing all four cases, if that makes sense to you.