server: Move all the top level files into cmd folder. (#2490)

This change brings a change which was done for the 'mc'
package to allow for clean repo and have a cleaner
github drop in experience.

cmd/api-response-multipart.go

@@ -0,0 +1,54 @@
+/*
+ * Minio Cloud Storage, (C) 2016 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Package cmd file carries any specific responses constructed/necessary in
+// multipart operations.
+package cmd
+
+import "net/http"
+
+// writeErrorResponsePartTooSmall - function is used specifically to
+// construct a proper error response during CompleteMultipartUpload
+// when one of the parts is < 5MB.
+// The requirement comes due to the fact that generic ErrorResponse
+// XML doesn't carry the additional fields required to send this
+// error. So we construct a new type which lies well within the scope
+// of this function.
+func writePartSmallErrorResponse(w http.ResponseWriter, r *http.Request, err PartTooSmall) {
+	// Represents additional fields necessary for ErrPartTooSmall S3 error.
+	type completeMultipartAPIError struct {
+		// Proposed size represents uploaded size of the part.
+		ProposedSize int64
+		// Minimum size allowed epresents the minimum size allowed per
+		// part. Defaults to 5MB.
+		MinSizeAllowed int64
+		// Part number of the part which is incorrect.
+		PartNumber int
+		// ETag of the part which is incorrect.
+		PartETag string
+		// Other default XML error responses.
+		APIErrorResponse
+	}
+	// Generate complete multipart error response.
+	errorResponse := getAPIErrorResponse(getAPIError(toAPIErrorCode(err)), r.URL.Path)
+	cmpErrResp := completeMultipartAPIError{err.PartSize, int64(5242880), err.PartNumber, err.PartETag, errorResponse}
+	encodedErrorResponse := encodeResponse(cmpErrResp)
+	// Write error body
+	w.Write(encodedErrorResponse)
+	w.(http.Flusher).Flush()
+}
+
+// Add any other multipart specific responses here.