Add raw blob endpoint to get objects by SHA ID (#5334)

* Add raw blob endpoint

This should make it possible to download raw blobs directly from
/:repo/:username/raw/blob/:sha1 URLs.

* fix: Make it work

* As an SHA-ID is no path getRefNameFromPath can't be used to verify
file specifying parameter
* added relevant change in go-gitea/git #132

Signed-off-by: Berengar W. Lehr <Berengar.Lehr@kompetenztest.de>

* Update Gopkg.lock

Can't update all vendors due to errors

Signed-off-by: Berengar W. Lehr <Berengar.Lehr@kompetenztest.de>

* style: Add Gitea copyright header

* feat: Added integration test for /repo/u/r/raw/blob

* fix: correct year in copyright header

vendor/code.gitea.io/git/repo_blob.go

@@ -0,0 +1,30 @@
+// Copyright 2018 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 git
+
+func (repo *Repository) getBlob(id SHA1) (*Blob, error) {
+	if _, err := NewCommand("cat-file", "-p", id.String()).RunInDir(repo.Path); err != nil {
+		return nil, ErrNotExist{id.String(), ""}
+	}
+
+	return &Blob{
+		repo: repo,
+		TreeEntry: &TreeEntry{
+			ID: id,
+			ptree: &Tree{
+				repo: repo,
+			},
+		},
+	}, nil
+}
+
+// GetBlob finds the blob object in the repository.
+func (repo *Repository) GetBlob(idStr string) (*Blob, error) {
+	id, err := NewIDFromString(idStr)
+	if err != nil {
+		return nil, err
+	}
+	return repo.getBlob(id)
+}