(WIP) Release branches and cherry picking

[ARR4N]

Let there be some set S of upstream commits, say S = {G3,G6,G8}, for which we wish the functionality to be included in libevm releases.; i.e. in all release branches, the S commits are included in the history. The difference lies in how each commit is introduced, either through:

1. Cherry-picking onto a release branch (never main), depicted as square commits; or
2. Being in the libevm history due to a merge of upstream code.

Invariants:

1. Cherry-picked commits are in order;
2. Exactly one copy of a commit, original or cherry-picked exists on a release branch; and
3. As a corollary of the single-version invariant: cherry-picking MUST NOT be performed on main.

Assuming S hasn't grown, creating a new release is therefore equivalent to an interactive rebase of an old release onto the tip of main. If main already includes a previously cherry-picked commit then it is dropped in the rebase, otherwise it is picked. The rebase is therefore monotonic from drop to pick because of invariant (1). If S grows then the new commits are cherry-picked after the rebase, i.f.f. necessary per invariant (2).

A single Rx commit exists at the tip of each release branch for chore changes like updating params.LibEVMVersion. These MUST be dropped during a new-release rebase.

Note

1. Branches release0 and release1 are graphically out of order solely to avoid confusing graph intersections.
2. The libevm branch is called main in the repo, but labelled differently here to ease understanding.

---
config:
  gitGraph:
    mainBranchName: geth
    parallelCommits: true
---
gitGraph TB:
    commit id: "G0"
    commit id: "G1"
    branch libevm order: 1
    commit id: "L0"
    commit id: "L1"
    checkout geth
    commit id: "G2"
    commit id: "G3"
    commit id: "G4"
    commit id: "G5"
    commit id: "G6"
    checkout libevm
    branch release0 order: 3
    commit id:"G3_0" type: HIGHLIGHT
    commit id:"G6_0" type: HIGHLIGHT
    commit id:"G8_0" type: HIGHLIGHT
    commit id: "R0" tag: "release-0"
    checkout libevm
    commit id: "L2"
    commit id: "L3"
    branch release1 order: 2
    commit id:"G3_1" type: HIGHLIGHT
    commit id:"G6_1" type: HIGHLIGHT
    commit id:"G8_1" type: HIGHLIGHT
    commit id: "R1" tag: "release-1"
    checkout geth
    commit id: "G7"
    checkout libevm
    commit id: "L4"
    merge geth
    checkout geth
    commit id: "G8"
    commit id: "G9"
    checkout libevm
    commit id: "L5"
    commit id: "L6"
    branch release2 order: 4
    commit id:"G8_2" type: HIGHLIGHT
    commit id: "R2" tag: "release-2"
    checkout libevm
    commit id: "L7"
    merge geth
    commit id: "L8"
    commit id: "L9"
    branch release3 order: 5
    commit id: "R3" tag: "release-3"

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