copy.c: make copy_fd preserve meaningful errnosb/copy-fd-errnorb/small-pieces-first

Update copy_fd to return a meaningful errno on failure and also
preserve the existing errno variable.

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

1 files changed, 10 insertions, 5 deletions

diff --git a/copy.c b/copy.c
index f2970ec462..a8d366eed4 100644
--- a/copy.c
+++ b/copy.c
@@ -8,12 +8,17 @@ int copy_fd(int ifd, int ofd)
 		if (!len)
 			break;
 		if (len < 0) {
-			return error("copy-fd: read returned %s",
-				     strerror(errno));
+			int save_errno = errno;
+			error("copy-fd: read returned %s", strerror(errno));
+			errno = save_errno;
+			return -1;
+		}
+		if (write_in_full(ofd, buffer, len) < 0) {
+			int save_errno = errno;
+			error("copy-fd: write returned %s", strerror(errno));
+			errno = save_errno;
+			return -1;
 		}
-		if (write_in_full(ofd, buffer, len) < 0)
-			return error("copy-fd: write returned %s",
-				     strerror(errno));
 	}
 	return 0;
 }