ADR 076: Combine Spec and Tendermint Repositories

Changelog

2022-02-04: Initial Draft. (@tychoish)

Status

Accepted.

Context

While the specification for Tendermint was originally in the same repository as the Go implementation, at some point the specification was split from the core repository and maintained separately from the implementation. While this makes sense in promoting a conceptual separation of specification and implementation, in practice this separation was a premature optimization, apparently aimed at supporting alternate implementations of Tendermint.

The operational and documentary burden of maintaining a separate spec repo has not returned value to justify its cost. There are no active projects to develop alternate implementations of Tendermint based on the common specification, and having separate repositories creates an ongoing burden to coordinate versions, documentation, and releases.

Decision

The specification repository will be merged back into the Tendermint core repository.

Stakeholders including representatives from the maintainers of the spec, the Go implementation, and the Tendermint Rust library, agreed to merge the repositories in the Tendermint core dev meeting on 27 January 2022, including @williambanfield @cmwaters @creachadair and @thanethomson.

Alternative Approaches

The main alternative we considered was to keep separate repositories, and to introduce a coordinated versioning scheme between the two, so that users could figure out which spec versions go with which versions of the core implementation.

We decided against this on the grounds that it would further complicate the release process for both repositories, without mitigating any of the other existing issues.

Detailed Design

Clone and merge the master branch of the tendermint/spec repository as a branch of the tendermint/tendermint, to ensure the commit history of both repositories remains intact.

Implementation Instructions

Within the tendermint repository, execute the following commands to add a new branch with the history of the master branch of spec:

git remote add spec git@github.com:tendermint/spec.git
git fetch spec
git checkout -b spec-master spec/master
mkdir spec
 git ls-tree -z --name-only HEAD | xargs -0 -I {} git mv {} subdir/
 git commit -m "spec: organize specification prior to merge"
 git checkout -b spec-merge-mainline origin/master
 git merge --allow-unrelated-histories spec-master

This merges the spec into the tendermint/tendermint repository as a normal branch. This commit can also be backported to the 0.35 branch, if needed.

Migrate outstanding issues from tendermint/spec to the tendermint/tendermint repository.
In the specification repository, add redirect to the README and mark the repository as archived.

Consequences

Positive

Easier maintenance for the specification will obviate a number of complicated and annoying versioning problems, and will help prevent the possibility of the specification and the implementation drifting apart.

Additionally, co-locating the specification will help encourage cross-pollination and collaboration, between engineers focusing on the specification and the protocol and engineers focusing on the implementation.

Negative

Co-locating the spec and Go implementation has the potential effect of prioritizing the Go implementation with regards to the spec, and making it difficult to think about alternate implementations of the Tendermint algorithm. Although we may want to foster additional Tendermint implementations in the future, this isn't an active goal in our current roadmap, and not merging these repos doesn't change the fact that the Go implementation of Tendermint is already the primary implementation.

Neutral

N/A

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