[PATCH 2/2] gcc8.1: fix strcat warning

[andy at warmcat.com (Andy Green)]

../ui-ssdiff.c: In function ?replace_tabs?:
../ui-ssdiff.c:142:4: warning: ?strncat? output truncated copying between 1 and 8 bytes from a string of length 8 [-Wstringop-truncation]
    strncat(result, spaces, 8 - (strlen(result) % 8));
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Actually the strncat that was there before intends that its
stock of spaces gets truncated, and it's not a problem.

However gcc8.1 is also right, normally truncation is undesirable.

Make the code do the padding explicitly.

Signed-off-by: Andy Green <andy at warmcat.com>
---
 ui-ssdiff.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/ui-ssdiff.c b/ui-ssdiff.c
index 7f261ed..e520b95 100644
--- a/ui-ssdiff.c
+++ b/ui-ssdiff.c
@@ -118,7 +118,6 @@ static char *replace_tabs(char *line)
 	int n_tabs = 0;
 	int i;
 	char *result;
-	char *spaces = "        ";
 
 	if (linelen == 0) {
 		result = xmalloc(1);
@@ -138,8 +137,17 @@ static char *replace_tabs(char *line)
 			strcat(result, prev_buf);
 			break;
 		} else {
+			char *p;
+			int n;
+
 			strncat(result, prev_buf, cur_buf - prev_buf);
-			strncat(result, spaces, 8 - (strlen(result) % 8));
+
+			n = strlen(result);
+			p = result + n;
+			n = 8 - (n % 8);
+			while (n--)
+				*p++ = ' ';
+			*p = '\0';
 		}
 		prev_buf = cur_buf + 1;
 	}