mailmap tests: add tests for empty "<>" syntax

Add tests for mailmap's handling of "<>", which is allowed on the RHS,
but not the LHS of a "<LHS> <RHS>" pair.

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

Author: avar

t/t4203-mailmap.sh

@@ -838,4 +838,31 @@ test_expect_success 'whitespace syntax: setup' '
 	test_cmp expect actual
 '
 
+test_expect_success 'empty syntax: setup' '
+	test_create_repo empty &&
+	test_commit -C empty --author "A <>" A &&
+	test_commit -C empty --author "B <[email protected]>" B &&
+	test_commit -C empty --author "C <[email protected]>" C &&
+
+	test_config -C empty mailmap.file ../empty.map &&
+	cat >>empty.map <<-\EOF &&
+	Ah <[email protected]> <>
+	Bee <[email protected]> <>
+	Cee <> <[email protected]>
+	EOF
+
+	cat >expect <<-\EOF &&
+	Author A <> maps to Bee <[email protected]>
+	Committer C O Mitter <[email protected]> maps to C O Mitter <[email protected]>
+
+	Author B <[email protected]> maps to B <[email protected]>
+	Committer C O Mitter <[email protected]> maps to C O Mitter <[email protected]>
+
+	Author C <[email protected]> maps to C <[email protected]>
+	Committer C O Mitter <[email protected]> maps to C O Mitter <[email protected]>
+	EOF
+	git -C empty 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