log: prevent error if line range ends past end of file

If the -L option is used to specify a line range in git log, and the end
of the range is past the end of the file, git will fail with a fatal
error. This commit prevents such behaviour - instead we perform the log
for existing lines within the specified range.

This commit also fixes a corner case where -L ,-n:file would be treated
as a log over the whole file. Now we treat this as -L 1,-n:file and
blame the first line of the file instead.

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

line-log.c

@@ -599,11 +599,11 @@ parse_lines(struct commit *commit, const char *prefix, struct string_list *args)
 				    lines, anchor, &begin, &end,
 				    full_name))
 			die("malformed -L argument '%s'", range_part);
-		if (lines < end || ((lines || begin) && lines < begin))
+		if ((!lines && (begin || end)) || lines < begin)
 			die("file %s has only %lu lines", name_part, lines);
 		if (begin < 1)
 			begin = 1;
-		if (end < 1)
+		if (end < 1 || lines < end)
 			end = lines;
 		begin--;
 		line_log_data_insert(&ranges, full_name, begin, end);

t/t4211-line-log.sh

@@ -60,7 +60,6 @@ test_bad_opts "-L 1:nonexistent" "There is no path"
 test_bad_opts "-L 1:simple" "There is no path"
 test_bad_opts "-L '/foo:b.c'" "argument not .start,end:file"
 test_bad_opts "-L 1000:b.c" "has only.*lines"
-test_bad_opts "-L 1,1000:b.c" "has only.*lines"
 test_bad_opts "-L :b.c" "argument not .start,end:file"
 test_bad_opts "-L :foo:b.c" "no match"
 
@@ -86,12 +85,12 @@ test_expect_success '-L ,Y (Y == nlines)' '
 
 test_expect_success '-L ,Y (Y == nlines + 1)' '
 	n=$(expr $(wc -l <b.c) + 1) &&
-	test_must_fail git log -L ,$n:b.c
+	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
+	git log -L ,$n:b.c
 '
 
 test_expect_success '-L with --first-parent and a merge' '