func prePushCheckForMissingObjects(pointers []*lfs.WrappedPointer) (objectsOnServer map[string]struct{}) {
	var missingLocalObjects []*lfs.WrappedPointer
	var missingSize int64
	var skipObjects = make(map[string]struct{}, len(pointers))
	for _, pointer := range pointers {
		if !lfs.ObjectExistsOfSize(pointer.Oid, pointer.Size) {
			// We think we need to push this but we don't have it
			// Store for server checking later
			missingLocalObjects = append(missingLocalObjects, pointer)
			missingSize += pointer.Size
		}
	}
	if len(missingLocalObjects) == 0 {
		return nil
	}

	checkQueue := lfs.NewDownloadCheckQueue(len(missingLocalObjects), missingSize, false)
	for _, p := range missingLocalObjects {
		checkQueue.Add(lfs.NewDownloadCheckable(p))
	}
	// this channel is filled with oids for which Check() succeeded & Transfer() was called
	transferc := checkQueue.Watch()
	go func() {
		for oid := range transferc {
			skipObjects[oid] = struct{}{}
		}
	}()
	checkQueue.Wait()
	return skipObjects
}

func prePushCheckForMissingObjects(pointers []*lfs.WrappedPointer) (objectsOnServer lfs.StringSet) {
	var missingLocalObjects []*lfs.WrappedPointer
	var missingSize int64
	var skipObjects = lfs.NewStringSetWithCapacity(len(pointers))
	for _, pointer := range pointers {
		if !lfs.ObjectExistsOfSize(pointer.Oid, pointer.Size) {
			// We think we need to push this but we don't have it
			// Store for server checking later
			missingLocalObjects = append(missingLocalObjects, pointer)
			missingSize += pointer.Size
		}
	}
	if len(missingLocalObjects) == 0 {
		return nil
	}

	checkQueue := lfs.NewDownloadCheckQueue(len(missingLocalObjects), missingSize, true)
	for _, p := range missingLocalObjects {
		checkQueue.Add(lfs.NewDownloadCheckable(p))
	}
	// this channel is filled with oids for which Check() succeeded & Transfer() was called
	transferc := checkQueue.Watch()
	done := make(chan int)
	go func() {
		for oid := range transferc {
			skipObjects.Add(oid)
		}
		done <- 1
	}()
	// Currently this is needed to flush the batch but is not enough to sync transferc completely
	checkQueue.Wait()
	<-done
	return skipObjects
}

func readyAndMissingPointers(allpointers []*lfs.WrappedPointer, include, exclude []string) ([]*lfs.WrappedPointer, []*lfs.WrappedPointer, int64) {
	size := int64(0)
	seen := make(map[string]bool, len(allpointers))
	missing := make([]*lfs.WrappedPointer, 0, len(allpointers))
	ready := make([]*lfs.WrappedPointer, 0, len(allpointers))

	for _, p := range allpointers {
		// Filtered out by --include or --exclude
		if !lfs.FilenamePassesIncludeExcludeFilter(p.Name, include, exclude) {
			continue
		}

		// no need to download the same object multiple times
		if seen[p.Oid] {
			continue
		}

		seen[p.Oid] = true

		// no need to download objects that exist locally already
		lfs.LinkOrCopyFromReference(p.Oid, p.Size)
		if lfs.ObjectExistsOfSize(p.Oid, p.Size) {
			ready = append(ready, p)
			continue
		}

		missing = append(missing, p)
		size += p.Size
	}

	return ready, missing, size
}

// Fetch and report completion of each OID to a channel (optional, pass nil to skip)
func fetchAndReportToChan(pointers []*lfs.WrappedPointer, include, exclude []string, out chan<- *lfs.WrappedPointer) {

	totalSize := int64(0)
	for _, p := range pointers {
		totalSize += p.Size
	}
	q := lfs.NewDownloadQueue(len(pointers), totalSize, false)

	for _, p := range pointers {
		// Only add to download queue if local file is not the right size already
		// This avoids previous case of over-reporting a requirement for files we already have
		// which would only be skipped by PointerSmudgeObject later
		passFilter := lfs.FilenamePassesIncludeExcludeFilter(p.Name, include, exclude)
		if !lfs.ObjectExistsOfSize(p.Oid, p.Size) && passFilter {
			q.Add(lfs.NewDownloadable(p))
		} else {
			// If we already have it, or it won't be fetched
			// report it to chan immediately to support pull/checkout
			if out != nil {
				out <- p
			}

		}
	}

	if out != nil {
		dlwatch := q.Watch()

		go func() {
			// fetch only reports single OID, but OID *might* be referenced by multiple
			// WrappedPointers if same content is at multiple paths, so map oid->slice
			oidToPointers := make(map[string][]*lfs.WrappedPointer, len(pointers))
			for _, pointer := range pointers {
				plist := oidToPointers[pointer.Oid]
				oidToPointers[pointer.Oid] = append(plist, pointer)
			}

			for oid := range dlwatch {
				plist, ok := oidToPointers[oid]
				if !ok {
					continue
				}
				for _, p := range plist {
					out <- p
				}
			}
			close(out)
		}()

	}
	processQueue := time.Now()
	q.Wait()
	tracerx.PerformanceSince("process queue", processQueue)
}

func (c *uploadContext) prepareUpload(unfiltered []*lfs.WrappedPointer) (*lfs.TransferQueue, []*lfs.WrappedPointer) {
	numUnfiltered := len(unfiltered)
	uploadables := make([]*lfs.WrappedPointer, 0, numUnfiltered)
	missingLocalObjects := make([]*lfs.WrappedPointer, 0, numUnfiltered)
	numObjects := 0
	totalSize := int64(0)
	missingSize := int64(0)

	// separate out objects that _should_ be uploaded, but don't exist in
	// .git/lfs/objects. Those will skipped if the server already has them.
	for _, p := range unfiltered {
		// object already uploaded in this process, skip!
		if c.HasUploaded(p.Oid) {
			continue
		}

		numObjects += 1
		totalSize += p.Size

		if lfs.ObjectExistsOfSize(p.Oid, p.Size) {
			uploadables = append(uploadables, p)
		} else {
			// We think we need to push this but we don't have it
			// Store for server checking later
			missingLocalObjects = append(missingLocalObjects, p)
			missingSize += p.Size
		}
	}

	// check to see if the server has the missing objects.
	c.checkMissing(missingLocalObjects, missingSize)

	// build the TransferQueue, automatically skipping any missing objects that
	// the server already has.
	uploadQueue := lfs.NewUploadQueue(numObjects, totalSize, c.DryRun)
	for _, p := range missingLocalObjects {
		if c.HasUploaded(p.Oid) {
			uploadQueue.Skip(p.Size)
		} else {
			uploadables = append(uploadables, p)
		}
	}

	return uploadQueue, uploadables
}