t4211: log: demonstrate -L bounds checking bug

A bounds checking bug allows the X in -LX to extend one line past the
end of file. For example, given a file with 5 lines, -L6 is accepted as
valid. Demonstrate this problem.

While here, also add tests to check that the remaining cases of X and Y
in -LX,Y are handled correctly at and in the vicinity of end-of-file.

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

t/t4211-line-log.sh

@@ -64,6 +64,36 @@ test_bad_opts "-L 1,1000:b.c" "has only.*lines"
 test_bad_opts "-L :b.c" "argument.*not of the form"
 test_bad_opts "-L :foo:b.c" "no match"
 
+test_expect_success '-L X (X == nlines)' '
+	n=$(wc -l <b.c) &&
+	git log -L $n:b.c
+'
+
+test_expect_failure '-L X (X == nlines + 1)' '
+	n=$(expr $(wc -l <b.c) + 1) &&
+	test_must_fail git log -L $n:b.c
+'
+
+test_expect_success '-L X (X == nlines + 2)' '
+	n=$(expr $(wc -l <b.c) + 2) &&
+	test_must_fail git log -L $n:b.c
+'
+
+test_expect_success '-L ,Y (Y == nlines)' '
+	n=$(printf "%d" $(wc -l <b.c)) &&
+	git log -L ,$n:b.c
+'
+
+test_expect_success '-L ,Y (Y == nlines + 1)' '
+	n=$(expr $(wc -l <b.c) + 1) &&
+	test_must_fail git log -L ,$n:b.c
+'
+
+test_expect_success '-L ,Y (Y == nlines + 2)' '
+	n=$(expr $(wc -l <b.c) + 2) &&
+	test_must_fail git log -L ,$n:b.c
+'
+
 # There is a separate bug when an empty -L range is the first -L encountered,
 # thus to demonstrate this particular bug, the empty -L range must follow a
 # non-empty -L range.