make_absolute_path(): Do not append redundant slash

When concatenating two paths, if the first one already have '/', do
not put another '/' in between the two paths.

Usually this is not the case as getcwd() won't return '/foo/bar/',
except when you are standing at root, then it will return '/'.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

abspath.c

@@ -54,8 +54,9 @@ const char *make_absolute_path(const char *path)
 			if (len + strlen(last_elem) + 2 > PATH_MAX)
 				die ("Too long path name: '%s/%s'",
 						buf, last_elem);
-			buf[len] = '/';
-			strcpy(buf + len + 1, last_elem);
+			if (len && buf[len-1] != '/')
+				buf[len++] = '/';
+			strcpy(buf + len, last_elem);
 			free(last_elem);
 			last_elem = NULL;
 		}