Add LFS Migration and Mirror (#14726)

* Implemented LFS client.

* Implemented scanning for pointer files.

* Implemented downloading of lfs files.

* Moved model-dependent code into services.

* Removed models dependency. Added TryReadPointerFromBuffer.

* Migrated code from service to module.

* Centralised storage creation.

* Removed dependency from models.

* Moved ContentStore into modules.

* Share structs between server and client.

* Moved method to services.

* Implemented lfs download on clone.

* Implemented LFS sync on clone and mirror update.

* Added form fields.

* Updated templates.

* Fixed condition.

* Use alternate endpoint.

* Added missing methods.

* Fixed typo and make linter happy.

* Detached pointer parser from gogit dependency.

* Fixed TestGetLFSRange test.

* Added context to support cancellation.

* Use ReadFull to probably read more data.

* Removed duplicated code from models.

* Moved scan implementation into pointer_scanner_nogogit.

* Changed method name.

* Added comments.

* Added more/specific log/error messages.

* Embedded lfs.Pointer into models.LFSMetaObject.

* Moved code from models to module.

* Moved code from models to module.

* Moved code from models to module.

* Reduced pointer usage.

* Embedded type.

* Use promoted fields.

* Fixed unexpected eof.

* Added unit tests.

* Implemented migration of local file paths.

* Show an error on invalid LFS endpoints.

* Hide settings if not used.

* Added LFS info to mirror struct.

* Fixed comment.

* Check LFS endpoint.

* Manage LFS settings from mirror page.

* Fixed selector.

* Adjusted selector.

* Added more tests.

* Added local filesystem migration test.

* Fixed typo.

* Reset settings.

* Added special windows path handling.

* Added unit test for HTTPClient.

* Added unit test for BasicTransferAdapter.

* Moved into util package.

* Test if LFS endpoint is allowed.

* Added support for git://

* Just use a static placeholder as the displayed url may be invalid.

* Reverted to original code.

* Added "Advanced Settings".

* Updated wording.

* Added discovery info link.

* Implemented suggestion.

* Fixed missing format parameter.

* Added Pointer.IsValid().

* Always remove model on error.

* Added suggestions.

* Use channel instead of array.

* Update routers/repo/migrate.go

* fmt

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: zeripath <art27@cantab.net>

modules/lfs/transferadapter.go

@@ -0,0 +1,58 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package lfs
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+)
+
+// TransferAdapter represents an adapter for downloading/uploading LFS objects
+type TransferAdapter interface {
+	Name() string
+	Download(ctx context.Context, r *ObjectResponse) (io.ReadCloser, error)
+	//Upload(ctx context.Context, reader io.Reader) error
+}
+
+// BasicTransferAdapter implements the "basic" adapter
+type BasicTransferAdapter struct {
+	client *http.Client
+}
+
+// Name returns the name of the adapter
+func (a *BasicTransferAdapter) Name() string {
+	return "basic"
+}
+
+// Download reads the download location and downloads the data
+func (a *BasicTransferAdapter) Download(ctx context.Context, r *ObjectResponse) (io.ReadCloser, error) {
+	download, ok := r.Actions["download"]
+	if !ok {
+		return nil, errors.New("lfs.BasicTransferAdapter.Download: Action 'download' not found")
+	}
+
+	req, err := http.NewRequestWithContext(ctx, "GET", download.Href, nil)
+	if err != nil {
+		return nil, fmt.Errorf("lfs.BasicTransferAdapter.Download http.NewRequestWithContext: %w", err)
+	}
+	for key, value := range download.Header {
+		req.Header.Set(key, value)
+	}
+
+	res, err := a.client.Do(req)
+	if err != nil {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+		return nil, fmt.Errorf("lfs.BasicTransferAdapter.Download http.Do: %w", err)
+	}
+
+	return res.Body, nil
+}