feat: add VersionedSMT for historical queries

[h5law]

Description

Summary generated by Reviewpad on 03 Sep 23 16:34 UTC

This pull request includes changes in multiple files:

1. The go.mod file was updated to change the Go version to 1.20 and add a new dependency on golang.org/x/exp v0.0.0-20230817173708-d852ddb80c63 while removing the dependency on github.com/google/go-cmp v0.5.8.

2. The file immutable.go introduces a new type ImmutableTree that wraps the SMT struct. It also implements various methods related to the immutable behavior of the tree, such as Update, Delete, Commit, and SetInitialVersion. Additionally, it provides methods for versions and retrieval of data based on versions.

3. The file diff introduces a new interface called VersionedSMT, which extends the SparseMerkleTree interface and adds methods for versioning and managing previous versions of the tree. It also introduces the TreeSpec struct with a helper function for custom hashers.

4. The file .github/workflows/test.yml was modified to update the TARGET_GOLANG_VERSION environment variable and the go version in both jobs.

5. The file diff for badgerKVStore.go includes the addition of the bytes package import, a new method called Clone in the badgerKVStore struct, and updates to comments and existing code.

6. The file diff introduces a new file encoding.go with functions related to encoding and decoding of stored trees using gob encoding.

7. The file Versioned.md includes changes related to the introduction and implementation details of the VersionedSMT interface, the VersionedTree and ImmutableTree types, and database lifecycle details.

8. The file diff for the test file includes test functions for an immutable tree, covering various scenarios and functionalities.

9. The file diff for utils.go includes new functions and imports related to numeric directory handling and directory existence checks.

10. The file diff introduces a new test file versioned_test.go with multiple test functions for a versioned tree.

11. The file diff for smt_utils_test.go includes changes related to introducing hashing capabilities in the code.

12. The file README.md includes changes in the required Go version and additional subsections.

13. The file encoding_test.go contains test functions for encoding and decoding a stored tree.

14. The file go.sum contains changes to the dependencies.

15. The file hasher.go includes changes related to the PathHasher, ValueHasher, treeHasher, pathHasher, and valueHasher types.

Please review these changes carefully.

Issue

Fixes N/A

Type of change

Please mark the relevant option(s):

• New feature, functionality or library
• Bug fix
• Code health or cleanup
• Major breaking change
• Documentation
• Other

List of changes

• Add VersionedSMT interface and ImmutableTree and VersionedTree implementations to wrap the SMT
• Allow for historical queries of a versioned SMT

Testing

• Task specific tests or benchmarks: go test ...
• New tests or benchmarks: go test ...
• All tests: go test -v

Required Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added, or updated, godoc format comments on touched members (see: tip.golang.org/doc/comment)
• I have tested my changes using the available tooling

If Applicable Checklist

• Update any relevant README(s)
• Add or update any relevant or supporting mermaid diagrams
• I have added tests that prove my fix is effective or that my feature works

[codecov]

Codecov Report

Patch coverage: 58.22% and project coverage change: -5.78% ⚠️

Comparison is base (2876295) 84.89% compared to head (24f7db0) 79.11%.

Additional details and impacted files

@@             Coverage Diff             @@
##           kvstore      #20      +/-   ##
===========================================
- Coverage    84.89%   79.11%   -5.78%     
===========================================
  Files            8       11       +3     
  Lines         1092     1408     +316     
===========================================
+ Hits           927     1114     +187     
- Misses         122      219      +97     
- Partials        43       75      +32     

Files Changed	Coverage Δ
types.go	87.91% <0.00%> (-5.12%)	⬇️
kvstore.go	67.17% <30.76%> (-1.47%)	⬇️
versioned.go	50.00% <50.00%> (ø)
hasher.go	99.07% <66.66%> (-0.93%)	⬇️
encoding.go	70.00% <70.00%> (ø)
utils.go	92.50% <86.95%> (-1.32%)	⬇️
immutable.go	100.00% <100.00%> (ø)

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[Olshansk]

@h5law Is this still a high priority?

[h5law]

@Olshansk No this is not priority anymore afaik

[Olshansk]

Let's close this out if its no longer relevant

[h5law]

This PR is no longer needed closing