blame: prevent error if range ends past end of file

If the -L option is used to specify a line range in git blame, and the
end of the range is past the end of the file, git will fail with a fatal
error. This commit prevents such behavior - instead we display the blame
for existing lines within the specified range. Tests are amended
accordingly.

This commit also fixes two corner cases. Blaming -L n,-(n+1) now blames
the first n lines of a file rather than from n to the end of the file.
Blaming -L ,-n will be treated as -L 1,-n and blame the first line of
the file, rather than blaming the whole file.

Signed-off-by: Isabella Stephens <istephens@atlassian.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: istephens

builtin/blame.c

@@ -886,13 +886,13 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
 				    nth_line_cb, &sb, lno, anchor,
 				    &bottom, &top, sb.path))
 			usage(blame_usage);
-		if (lno < top || ((lno || bottom) && lno < bottom))
+		if ((!lno && (top || bottom)) || lno < bottom)
 			die(Q_("file %s has only %lu line",
 			       "file %s has only %lu lines",
 			       lno), path, lno);
 		if (bottom < 1)
 			bottom = 1;
-		if (top < 1)
+		if (top < 1 || lno < top)
 			top = lno;
 		bottom--;
 		range_set_append_unsafe(&ranges, bottom, top);

line-range.c

@@ -47,7 +47,7 @@ static const char *parse_loc(const char *spec, nth_line_fn_t nth_line,
 			else if (!num)
 				*ret = begin;
 			else
-				*ret = begin + num;
+				*ret = begin + num > 0 ? begin + num : 1;
 			return term;
 		}
 		return spec;

t/annotate-tests.sh

@@ -320,11 +320,11 @@ test_expect_success 'blame -L ,Y (Y == nlines)' '
 
 test_expect_success 'blame -L ,Y (Y == nlines + 1)' '
 	n=$(expr $(wc -l <file) + 2) &&
-	test_must_fail $PROG -L,$n file
+	check_count -L,$n A 1 B 1 B1 1 B2 1 "A U Thor" 1 C 1 D 1 E 1
 '
 
 test_expect_success 'blame -L ,Y (Y > nlines)' '
-	test_must_fail $PROG -L,12345 file
+	check_count -L,12345 A 1 B 1 B1 1 B2 1 "A U Thor" 1 C 1 D 1 E 1
 '
 
 test_expect_success 'blame -L multiple (disjoint)' '

t/t8003-blame-corner-cases.sh

@@ -216,14 +216,18 @@ test_expect_success 'blame -L with invalid start' '
 '
 
 test_expect_success 'blame -L with invalid end' '
-	test_must_fail git blame -L1,5 tres 2>errors &&
-	test_i18ngrep "has only 2 lines" errors
+	git blame -L1,5 tres >out &&
+	test_line_count = 2 out
 '
 
 test_expect_success 'blame parses <end> part of -L' '
 	git blame -L1,1 tres >out &&
-	cat out &&
-	test $(wc -l < out) -eq 1
+	test_line_count = 1 out
+'
+
+test_expect_success 'blame -Ln,-(n+1)' '
+	git blame -L3,-4 nine_lines >out &&
+	test_line_count = 3 out
 '
 
 test_expect_success 'indent of line numbers, nine lines' '