mailmap tests: add a test for comment syntax

Add a test for mailmap comment syntax. As noted in [1] there was no
test coverage for this. Let's make sure a future change doesn't break
it.

1. https://lore.kernel.org/git/CAN0heSoKYWXqskCR=GPreSHc6twCSo1345WTmiPdrR57XSShhA@mail.gmail.com/

Reported-by: Martin Ågren <[email protected]>
Signed-off-by: Ævar Arnfjörð Bjarmason <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: avar

t/t4203-mailmap.sh

@@ -753,4 +753,37 @@ test_expect_success 'commit --author honors mailmap' '
 	test_cmp expect actual
 '
 
+test_expect_success 'comment syntax: setup' '
+	test_create_repo comm &&
+	test_commit -C comm --author "A <[email protected]>" A &&
+	test_commit -C comm --author "B <[email protected]>" B &&
+	test_commit -C comm --author "C <#@example.com>" C &&
+	test_commit -C comm --author "D <d@e#ample.com>" D &&
+
+	test_config -C comm mailmap.file ../doc.map &&
+	cat >>doc.map <<-\EOF &&
+	# Ah <[email protected]>
+
+	; Bee <[email protected]>
+	Cee <[email protected]> <#@example.com>
+	Dee <[email protected]> <d@e#ample.com>
+	EOF
+
+	cat >expect <<-\EOF &&
+	Author A <[email protected]> maps to A <[email protected]>
+	Committer C O Mitter <[email protected]> maps to C O Mitter <[email protected]>
+
+	Author B <[email protected]> maps to ; Bee <[email protected]>
+	Committer C O Mitter <[email protected]> maps to C O Mitter <[email protected]>
+
+	Author C <#@example.com> maps to Cee <[email protected]>
+	Committer C O Mitter <[email protected]> maps to C O Mitter <[email protected]>
+
+	Author D <d@e#ample.com> maps to Dee <[email protected]>
+	Committer C O Mitter <[email protected]> maps to C O Mitter <[email protected]>
+	EOF
+	git -C comm log --reverse --pretty=format:"Author %an <%ae> maps to %aN <%aE>%nCommitter %cn <%ce> maps to %cN <%cE>%n" >actual &&
+	test_cmp expect actual
+'
+
 test_done