blame: fix -L bounds checking bug

Since inception, -LX,Y has correctly reported an out-of-range error when
Y is beyond end of file, however, X was not checked, and an out-of-range
X would cause a crash.  92f9e27 (blame: prevent a segv when -L given
start > EOF; 2010-02-08) attempted to rectify this shortcoming but has
its own off-by-one error which allows X to extend one line past end of
file.  For example, given a file with 5 lines:

  git blame -L5 foo  # OK, blames line 5
  git blame -L6 foo  # accepted, no error, no output, huh?
  git blame -L7 foo  # error "fatal: file foo has only 5 lines"

Fix this bug.

In order to avoid regressing "blame foo" when foo is an empty file, the
fix is slightly more complicated than changing '<' to '<='.

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

builtin/blame.c

@@ -2495,13 +2495,13 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
 	bottom = top = 0;
 	if (bottomtop)
 		prepare_blame_range(&sb, bottomtop, lno, &bottom, &top);
+	if (lno < top || ((lno || bottom) && lno < bottom))
+		die("file %s has only %lu lines", path, lno);
 	if (bottom < 1)
 		bottom = 1;
 	if (top < 1)
 		top = lno;
 	bottom--;
-	if (lno < top || lno < bottom)
-		die("file %s has only %lu lines", path, lno);
 
 	ent = xcalloc(1, sizeof(*ent));
 	ent->lno = bottom;

t/annotate-tests.sh

@@ -232,7 +232,7 @@ test_expect_success 'blame -L X (X == nlines)' '
 	check_count -L$n C 1
 '
 
-test_expect_failure 'blame -L X (X == nlines + 1)' '
+test_expect_success 'blame -L X (X == nlines + 1)' '
 	n=$(expr $(wc -l <file) + 2) &&
 	test_must_fail $PROG -L$n file
 '
@@ -321,7 +321,7 @@ test_expect_success 'blame -L 0 empty (undocumented)' '
 	check_count -h HEAD^^ -f incremental -L0
 '
 
-test_expect_failure 'blame -L 1 empty' '
+test_expect_success 'blame -L 1 empty' '
 	test_must_fail $PROG -L1 incremental HEAD^^
 '
 
@@ -341,7 +341,7 @@ test_expect_success 'blame -L 1 half' '
 	check_count -h HEAD^ -f incremental -L1 I 1
 '
 
-test_expect_failure 'blame -L 2 half' '
+test_expect_success 'blame -L 2 half' '
 	test_must_fail $PROG -L2 incremental HEAD^
 '
 
@@ -361,7 +361,7 @@ test_expect_success 'blame -L 1 full' '
 	check_count -f incremental -L1 I 1
 '
 
-test_expect_failure 'blame -L 2 full' '
+test_expect_success 'blame -L 2 full' '
 	test_must_fail $PROG -L2 incremental
 '