t8001/t8002: blame: add empty file & partial-line tests

Add boundary case tests, with and without -L, for empty file; file with
one partial line; file with one full line.

The empty file test without -L is of particular interest. Historically,
this case has been supported (empty blame output) and this test protects
against regression by a subsequent patch fixing an off-by-one bug which
incorrectly accepts -LX where X is one past end-of-file.

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/annotate-tests.sh

@@ -297,6 +297,78 @@ test_expect_success 'blame -L :nomatch' '
 	test_must_fail $PROG -L:nomatch hello.c
 '
 
+test_expect_success 'setup incremental' '
+	(
+	GIT_AUTHOR_NAME=I &&
+	export GIT_AUTHOR_NAME &&
+	GIT_AUTHOR_EMAIL=I@test.git &&
+	export GIT_AUTHOR_EMAIL &&
+	>incremental &&
+	git add incremental &&
+	git commit -m "step 0" &&
+	printf "partial" >>incremental &&
+	git commit -a -m "step 0.5" &&
+	echo >>incremental &&
+	git commit -a -m "step 1"
+	)
+'
+
+test_expect_success 'blame empty' '
+	check_count -h HEAD^^ -f incremental
+'
+
+test_expect_success 'blame -L 0 empty (undocumented)' '
+	check_count -h HEAD^^ -f incremental -L0
+'
+
+test_expect_failure 'blame -L 1 empty' '
+	test_must_fail $PROG -L1 incremental HEAD^^
+'
+
+test_expect_success 'blame -L 2 empty' '
+	test_must_fail $PROG -L2 incremental HEAD^^
+'
+
+test_expect_success 'blame half' '
+	check_count -h HEAD^ -f incremental I 1
+'
+
+test_expect_success 'blame -L 0 half (undocumented)' '
+	check_count -h HEAD^ -f incremental -L0 I 1
+'
+
+test_expect_success 'blame -L 1 half' '
+	check_count -h HEAD^ -f incremental -L1 I 1
+'
+
+test_expect_failure 'blame -L 2 half' '
+	test_must_fail $PROG -L2 incremental HEAD^
+'
+
+test_expect_success 'blame -L 3 half' '
+	test_must_fail $PROG -L3 incremental HEAD^
+'
+
+test_expect_success 'blame full' '
+	check_count -f incremental I 1
+'
+
+test_expect_success 'blame -L 0 full (undocumented)' '
+	check_count -f incremental -L0 I 1
+'
+
+test_expect_success 'blame -L 1 full' '
+	check_count -f incremental -L1 I 1
+'
+
+test_expect_failure 'blame -L 2 full' '
+	test_must_fail $PROG -L2 incremental
+'
+
+test_expect_success 'blame -L 3 full' '
+	test_must_fail $PROG -L3 incremental
+'
+
 test_expect_success 'blame -L' '
 	test_must_fail $PROG -L file
 '