run_processes_parallel: treat output of children as byte array

We do not want the output to be interrupted by a NUL byte, so we
cannot use raw fputs. Introduce strbuf_write to avoid having long
arguments in run-command.c.

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

strbuf.c

@@ -395,6 +395,12 @@ ssize_t strbuf_read_once(struct strbuf *sb, int fd, size_t hint)
 	return cnt;
 }
 
+ssize_t strbuf_write(struct strbuf *sb, FILE *f)
+{
+	return sb->len ? fwrite(sb->buf, 1, sb->len, f) : 0;
+}
+
+
 #define STRBUF_MAXLINK (2*PATH_MAX)
 
 int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)