t8001/t8002: blame: demonstrate -L bounds checking bug

t8001/t8002: blame: 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 <redacted>
Signed-off-by: Junio C Hamano <redacted>