t7810-grep: test --all-match with multiple --grep and --author options

The code used to have a bug that ignores "--all-match", that requires
all "--grep" to have matched, when "--author" or "--committer" was used.

Make sure the bug will not be reintroduced.

Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t7810-grep.sh

@@ -531,6 +531,16 @@ test_expect_success 'log --grep --grep --author takes union of greps and interse
 	test_cmp expect actual
 '
 
+test_expect_success 'log ---all-match -grep --author --author still takes union of authors and intersects with grep' '
+	# grep matches only initial and third
+	# author matches all but second
+	git log --all-match --author="Thor" --author="Night" --grep=i --format=%s >actual &&
+	{
+	    echo third && echo initial
+	} >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'log --grep --author --author takes union of authors and intersects with grep' '
 	# grep matches only initial and third
 	# author matches all but second
@@ -541,6 +551,16 @@ test_expect_success 'log --grep --author --author takes union of authors and int
 	test_cmp expect actual
 '
 
+test_expect_success 'log --all-match --grep --grep --author takes intersection' '
+	# grep matches only third
+	# author matches only initial and third
+	git log --all-match --author="A U Thor" --grep=i --grep=r --format=%s >actual &&
+	{
+		echo third
+	} >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'grep with CE_VALID file' '
 	git update-index --assume-unchanged t/t &&
 	rm t/t &&