path.c: Use vsnpath() in the implementation of git_path()

The current implementation of git_path() is essentially the same as
that of vsnpath(), with two minor differences. First, git_path()
currently insists that the git directory path is no longer than
PATH_MAX-100 characters in length. However, vsnpath() does not
attempt this arbitrary 100 character reservation for the remaining
path components. Second, vsnpath() uses the "is_dir_sep()" macro,
rather than comparing directly to '/', to determine if the git_dir
path component ends with a path separator.

In order to benefit from the above improvements, along with increased
compatability with git_snpath() and git_pathdup(), we reimplement the
git_path() function using vsnpath().

Signed-off-by: Ramsay Jones <ramsay@ramsay1.demon.co.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

path.c

@@ -119,23 +119,14 @@ char *mkpath(const char *fmt, ...)
 
 char *git_path(const char *fmt, ...)
 {
-	const char *git_dir = get_git_dir();
 	char *pathname = get_pathname();
 	va_list args;
-	unsigned len;
+	char *ret;
 
-	len = strlen(git_dir);
-	if (len > PATH_MAX-100)
-		return bad_path;
-	memcpy(pathname, git_dir, len);
-	if (len && git_dir[len-1] != '/')
-		pathname[len++] = '/';
 	va_start(args, fmt);
-	len += vsnprintf(pathname + len, PATH_MAX - len, fmt, args);
+	ret = vsnpath(pathname, PATH_MAX, fmt, args);
 	va_end(args);
-	if (len >= PATH_MAX)
-		return bad_path;
-	return cleanup_path(pathname);
+	return ret;
 }
 
 void home_config_paths(char **global, char **xdg, char *file)