send-email: fix a "first config key wins" regression in v2.33.0

Fix a regression in my c95e3a3 (send-email: move trivial config
handling to Perl, 2021-05-28) where we'd pick the first config key out
of multiple defined ones, instead of using the normal "last key wins"
semantics of "git config --get".

This broke e.g. cases where a .git/config would have a different
sendemail.smtpServer than ~/.gitconfig. We'd pick the ~/.gitconfig
over .git/config, instead of preferring the repository-local
version. The same would go for /etc/gitconfig etc.

The full list of impacted config keys (the %config_settings values
which are references to scalars, not arrays) is:

    sendemail.smtpencryption
    sendemail.smtpserver
    sendemail.smtpserverport
    sendemail.smtpuser
    sendemail.smtppass
    sendemail.smtpdomain
    sendemail.smtpauth
    sendemail.smtpbatchsize
    sendemail.smtprelogindelay
    sendemail.tocmd
    sendemail.cccmd
    sendemail.aliasfiletype
    sendemail.envelopesender
    sendemail.confirm
    sendemail.from
    sendemail.assume8bitencoding
    sendemail.composeencoding
    sendemail.transferencoding
    sendemail.sendmailcmd

I.e. having any of these set in say ~/.gitconfig and in-repo
.git/config regressed in v2.33.0 to prefer the --global one over the
--local.

To test this add a test of config priority to one of these config
variables, most don't have tests at all, but there was an existing one
for sendemail.8bitEncoding.

The "git config" (instead of "test_config") is somewhat of an
anti-pattern, but follows established conventions in
t9001-send-email.sh, likewise with any other pattern or idiom in this
test.

The populating of home/.gitconfig and setting of HOME= is copied from
a test in t0017-env-helper.sh added in 1ff750b (tests: make
GIT_TEST_GETTEXT_POISON a boolean, 2019-06-21). This test fails
without this bugfix, but now it works.

Reported-by: Eli Schwartz <[email protected]>
Tested-by: Eli Schwartz <[email protected]>
Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

git-send-email.perl

@@ -373,7 +373,7 @@ sub read_config {
 			@$target = @values;
 		}
 		else {
-			my $v = $known_keys->{$key}->[0];
+			my $v = $known_keys->{$key}->[-1];
 			next unless defined $v;
 			next if $configured->{$setting}++;
 			$$target = $v;

t/t9001-send-email.sh

@@ -1533,6 +1533,21 @@ test_expect_success $PREREQ 'sendemail.8bitEncoding works' '
 	test_cmp content-type-decl actual
 '
 
+test_expect_success $PREREQ 'sendemail.8bitEncoding in .git/config overrides --global .gitconfig' '
+	clean_fake_sendmail &&
+	git config sendemail.assume8bitEncoding UTF-8 &&
+	test_when_finished "rm -rf home" &&
+	mkdir home &&
+	git config -f home/.gitconfig sendemail.assume8bitEncoding "bogus too" &&
+	echo bogus |
+	env HOME="$(pwd)/home" DEBUG=1 \
+	git send-email [email protected] [email protected] \
+			--smtp-server="$(pwd)/fake.sendmail" \
+			email-using-8bit >stdout &&
+	egrep "Content|MIME" msgtxt1 >actual &&
+	test_cmp content-type-decl actual
+'
+
 test_expect_success $PREREQ '--8bit-encoding overrides sendemail.8bitEncoding' '
 	clean_fake_sendmail &&
 	git config sendemail.assume8bitEncoding "bogus too" &&