Fork cortex chunk storage into Loki.

[cyriltovena]

This PR forks cortex chunk package into our storage package since Cortex doesn't plan to use it anymore.

This will give us the ability to change object store client for hedging request for instance and include more fixes tailored for Loki.

I had to upgrade protobuf and gogoproto up to what Cortex is using. I've used subtree to maintain the history but that seems to make CLA not happy. @slim-bean WDYT ? do we care ?

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
10 out of 17 committers have signed the CLA.

✅ cyriltovena
✅ sandeepsukhani
✅ simonswine
✅ pstibrany
✅ pracucci
✅ jtlisi
✅ kminehart
✅ 56quarters
✅ aknuds1
✅ bboreham
❌ somdoron
❌ lucasvmiguel
❌ yeya24
❌ jakubgs
❌ ChinYing-Li
❌ ubcharron
❌ kamijin-fanta
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[sandeepsukhani]

I think we should maybe move pkg/storage/chunk/storage to pkg/storage but that can be done in another PR but I am not sure if we can retain the history. Overall the changes look good to me.

I think we should also decide on CLA before merging this.

[cyriltovena]

@sandeepsukhani it's easier to keep the same package name to avoid renaming everything.

[slim-bean]

It is not required to get the CLA signed by all previous contributors per my understanding.

However we should include and make clear the copyright information on the forked files (excluding vendored files).

Using the softwarefreedom.org guidance I suggest we add the following header to all incoming files (excluding the vendor directory):

/*  
 *   Grafana Loki
 *   Copyright (C) 2021 Grafana Labs
 *
 *   This program is free software: you can redistribute it and/or modify
 *   it under the terms of the GNU Affero General Public License as published by
 *   the Free Software Foundation, either version 3 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU Affero General Public License for more details.
 *
 *   You should have received a copy of the GNU Affero General Public License
 *   along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *  
 * This file incorporates work covered by the following copyright and  
 * permission notice:  
 *  
 *     Copyright 2016-2021 Cortex Project Contributors
 *
 *   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.
 */ 

Note: the Cortex copyright line was created using the CNCF Copyright Guidance

[slim-bean]

Through some further discussion I am revising my advice.

I do not think it is necessary to add any specific copyright notice, primarily referencing:

Copyright notices are not mandatory in order for the contributor to retain ownership of their copyright. [1]

As such the existing information in Git should be sufficient for determining copyright and that reason as well as the others listed on the CNCF copyright guidance[1] are enough for me to be convinced there is little value in adding a specific copyright to these files.

[1] https://github.com/cncf/foundation/blob/7845477c70fff46d61bad1b47c087a13bbcb259d/copyright-notices.md#why-not-list-every-copyright-holder

[RichiH]

I agree that sleuthing up all copyright holders is near-endless work and not of much benefit. I do think that cross-linking to make code, copyright, and legal spelunking easier is A Good Thing, though. What about a simple

/* SPDX-License-Identifier: AGPL-3.0-only
 * Forked-from: https://github.com/cortexproject/cortex @ commit 123
 */

and we can ask SPDX if they would consider standardizing more headers to allow for better cross-linking?