merge-recursive: eliminate flush_buffer() in favor of write_in_full()

flush_buffer() is a thin wrapper around write_in_full() with two very
confusing properties:

* It runs a loop to handle short reads, ensuring that we write
  everything.  But that is precisely what write_in_full() does!

* It checks for a return value of 0 from write_in_full(), which cannot
  happen: it returns this value only if count=0, but flush_buffer()
  will never call write_in_full() in this case.

Remove it.
Signed-off-by: NThomas Rast <trast@student.ethz.ch>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

merge-recursive.c

@@ -613,23 +613,6 @@ static char *unique_path(struct merge_options *o, const char *path, const char *
 	return newpath;
 }
 
-static void flush_buffer(int fd, const char *buf, unsigned long size)
-{
-	while (size > 0) {
-		long ret = write_in_full(fd, buf, size);
-		if (ret < 0) {
-			/* Ignore epipe */
-			if (errno == EPIPE)
-				break;
-			die_errno("merge-recursive");
-		} else if (!ret) {
-			die("merge-recursive: disk full?");
-		}
-		size -= ret;
-		buf += ret;
-	}
-}
-
 static int dir_in_way(const char *path, int check_working_copy)
 {
 	int pos, pathlen = strlen(path);
@@ -788,7 +771,7 @@ static void update_file_flags(struct merge_options *o,
 			fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, mode);
 			if (fd < 0)
 				die_errno("failed to open '%s'", path);
-			flush_buffer(fd, buf, size);
+			write_in_full(fd, buf, size);
 			close(fd);
 		} else if (S_ISLNK(mode)) {
 			char *lnk = xmemdupz(buf, size);