log tests: check if grep_config() is called by "log"-like cmds

Extend the tests added in my 9df46763ef (log: add exhaustive tests
for pattern style options & config, 2017-05-20) to check not only
whether "git log" handles "grep.patternType", but also "git show"
etc.

It's sufficient to check whether we match a "fixed" or a "basic" regex
here to see if these codepaths correctly invoked grep_config(). We
don't need to check the details of their regular expression matching
as the "log" test does.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t4202-log.sh

@@ -449,6 +449,30 @@ test_expect_success !FAIL_PREREQS 'log with various grep.patternType configurati
 	)
 '
 
+for cmd in show whatchanged reflog format-patch
+do
+	case "$cmd" in
+	format-patch) myarg="HEAD~.." ;;
+	*) myarg= ;;
+	esac
+
+	test_expect_success "$cmd: understands grep.patternType, like 'log'" '
+		git init "pattern-type-$cmd" &&
+		(
+			cd "pattern-type-$cmd" &&
+			test_commit 1 file A &&
+			test_commit "(1|2)" file B 2 &&
+
+			git -c grep.patternType=fixed $cmd --grep="..." $myarg >actual &&
+			test_must_be_empty actual &&
+
+			git -c grep.patternType=basic $cmd --grep="..." $myarg >actual &&
+			test_file_not_empty actual
+		)
+	'
+done
+test_done
+
 test_expect_success 'log --author' '
 	cat >expect <<-\EOF &&
 	Author: <BOLD;RED>A U<RESET> Thor <author@example.com>