streaming_write_entry: propagate streaming errors

When we are streaming an index blob to disk, we store the
error from stream_blob_to_fd in the "result" variable, and
then immediately overwrite that with the return value of
"close". That means we catch errors on close (e.g., problems
committing the file to disk), but miss anything which
happened before then.

We can fix this by using bitwise-OR to accumulate errors in
our result variable.

While we're here, we can also simplify the error handling
with an early return, which makes it easier to see under
which circumstances we need to clean up.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

entry.c

@@ -120,16 +120,18 @@ static int streaming_write_entry(struct cache_entry *ce, char *path,
 				 const struct checkout *state, int to_tempfile,
 				 int *fstat_done, struct stat *statbuf)
 {
-	int result = -1;
+	int result = 0;
 	int fd;
 
 	fd = open_output_fd(path, ce, to_tempfile);
-	if (0 <= fd) {
-		result = stream_blob_to_fd(fd, ce->sha1, filter, 1);
-		*fstat_done = fstat_output(fd, state, statbuf);
-		result = close(fd);
-	}
-	if (result && 0 <= fd)
+	if (fd < 0)
+		return -1;
+
+	result |= stream_blob_to_fd(fd, ce->sha1, filter, 1);
+	*fstat_done = fstat_output(fd, state, statbuf);
+	result |= close(fd);
+
+	if (result)
 		unlink(path);
 	return result;
 }

t/t1060-object-corruption.sh

@@ -24,6 +24,15 @@ test_expect_success 'setup corrupt repo' '
 	)
 '
 
+test_expect_success 'setup repo with missing object' '
+	git init missing &&
+	(
+		cd missing &&
+		test_commit content &&
+		rm -f "$(obj_to_file HEAD:content.t)"
+	)
+'
+
 test_expect_success 'streaming a corrupt blob fails' '
 	(
 		cd bit-error &&
@@ -31,4 +40,20 @@ test_expect_success 'streaming a corrupt blob fails' '
 	)
 '
 
+test_expect_success 'read-tree -u detects bit-errors in blobs' '
+	(
+		cd bit-error &&
+		rm -f content.t &&
+		test_must_fail git read-tree --reset -u HEAD
+	)
+'
+
+test_expect_success 'read-tree -u detects missing objects' '
+	(
+		cd missing &&
+		rm -f content.t &&
+		test_must_fail git read-tree --reset -u HEAD
+	)
+'
+
 test_done