ceremony/docs/UPSTREAM-SYNC.md

# Syncing this tree with upstream ceremony

`heavy-duty/ceremony` exists on two forges and they diverge in opposite
directions on purpose:

- **upstream** — `github.com/heavy-duty/ceremony`, where new ceremony features
  are written. **Read-only from here.** No issue, PR, comment, review or
  release is ever created there.
- **this tree** — `forgejo.heavyduty.builders/heavy-duty/ceremony`, which
  carries upstream's content plus the forge-compatibility delta and never
  writes back.

This document is the procedure for bringing upstream's work across. It is
written to be followed without prior context; where it states a resolution, the
resolution is standing and does not get re-decided each sync.

Worked example throughout: the `0.6.0` sync (#197, #198), which merged upstream
`8c3a4d1` onto `dad99dd` and took four heads to get green.

## The standing resolutions

These recur every sync. They are decided; re-deciding them is the cost this
list exists to remove.

| what | which side wins | decided by |
|---|---|---|
| `VERSION` | **upstream** — this tree tracks upstream's version numbers | #197 D2 |
| `CEREMONY_SELF_REF` (both carriers) | **upstream** | #197 D2 |
| `.github/labels.conf` | **this tree** — upstream's roster names identities that do not exist here | #195 |
| `drills/*.md` | **this tree** — a drill record is a record of a run *here* | #198 |
| `CHANGELOG.md` | **both**, upstream's new sections above this tree's | #198 |
| a section for a version **both** trees released | **this tree's** — ours is the published body of the tag that exists here | #198 |

Two consequences worth stating plainly:

- **Two trees answer to the same version number**, differing by the forge
  delta. That is accepted, not accidental (#197 D2). The mitigation is
  provenance in prose: `CHANGELOG.md`'s header names the upstream commit this
  tree carries, and `.upstream-ref` records it in machine-readable form.
- **A tag that exists upstream may not exist here.** `CEREMONY_SELF_REF` takes
  upstream's number, and both workflows carry the self-consumption bypass
  (`if: github.repository != 'heavy-duty/ceremony'`), so ceremony's own CI is
  unaffected. But **no consumer may bump its pin to that number until the
  release ceremony cuts the tag here.**

## The procedure

### 1. Add the upstream remote, read-only, and confirm the merge base

```sh
git remote add gh https://github.com/heavy-duty/ceremony.git   # if absent
git fetch gh
git merge-base main gh/main
```

**Confirm the merge base against `.upstream-ref` before merging anything.** If
it is not what the last sync recorded, something moved — stop and re-measure
rather than proceeding. A sync that starts from an unexpected base is a sync
whose conflict count means nothing.

### 2. Merge, never rebase

```sh
git merge gh/main
```

One merge commit, conflicts resolved once (#197 D1). Rebasing the forge-only
commits onto upstream would rewrite every SHA, re-resolve the same conflicts
once per commit, and break any pin to them. A fresh re-import would discard the
provenance in this repo's issue comments, which is where its documentation
actually lives.

### 3. Resolve the conflicts

Apply the standing resolutions above. What is left is genuinely new and needs
judgement — in the `0.6.0` sync that was 5 hunks of 18.

### 4. Audit what the merge brought in that did NOT conflict

**This is the step the `0.6.0` sync nearly shipped without, and the one this
document exists for.**

`git merge` takes upstream's side wherever only upstream moved a region. So a
function upstream *added* to a file this tree already owns arrives with **no
conflict and no question asked**. Reviewing the conflict hunks cannot find
them: four reviewers read the same diff and each found a different subset.

In the `0.6.0` sync that was **eight** runtime `gh` call sites, in three files
and two file types, every one of which #188 had previously removed.

So, after resolving:

```sh
bash test/no-runtime-gh.test.sh
```

That guard is the mechanical form of #197's acceptance bar — no runtime `gh`
outside `lib/forge-github.sh` unless the file declares
`CEREMONY_FORGE_CLIENT=gh` **and** refuses when it cannot run. Do not satisfy
it by adding an exemption; a declaration without a refusal is a permission slip
for `gh: command not found`.

Then check the **variables** the same way, because the same mechanic applies to
state: if a conflicted region assigns something that auto-merged code consumes,
resolving it "to this tree's side" silently removes the producer. Every one of
those consumers degrades to empty rather than erroring, so nothing goes red.
The `0.6.0` sync had three such seams. Enumerate what each resolved region
assigns, and confirm each still has a producer.

### 5. Port or declare every new `gh` call site

Where a `forge_*` verb exists, port it in the merge itself. Where none does,
the file **declares** `CEREMONY_FORGE_CLIENT=gh` and refuses loudly, and the
port gets its own issue (#199 for `refs-not-closing`, #205 for the sweep
dispatch). "Never 'probably github'" applies to the sync as much as to a
runtime probe.

A workflow cannot call `forge_preflight`, so it declares in its `env:` block
and refuses inline — deciding the **forge** first and the **binary** second. A
guard that only asks whether `gh` is installed passes the moment a runner image
ships it.

### 6. Record the provenance

- `CHANGELOG.md`'s header: which upstream commit this tree now carries.
- `.upstream-ref`: the same SHA, machine-readable, checked by
  `test/upstream-delta.test.sh`.
- A `changelog.d/` fragment for the sync issue.

### 7. Verify — and verify where it will actually run

`test/run.sh` green on your machine is the weakest of the checks below. The
`0.6.0` sync was "green locally" and red on the runner **three times, for three
different reasons**:

| what was green locally | why the runner disagreed |
|---|---|
| `shellcheck-all.sh` | it lints **tracked** files, and the new guard was untracked |
| the whole suite | CI pins **shellcheck 0.10.0**; a different local version reports differently |
| `issue_payload_valid` | `jq -e` on empty input exits **4** on jq 1.7 and **0** on jq 1.6 — and the runner image ships 1.6 |

That last one was not a test problem: on jq 1.6 the guard that refuses an
unreadable read was *accepting* one. **The distance between your environment
and the runner's is part of the sync's risk surface, not an inconvenience.**

So verify with the runner's own tooling:

```sh
git add -A                                        # or shellcheck sees nothing new
CEREMONY_REQUIRE_NPM=1 CEREMONY_REQUIRE_YQ=1 bash test/run.sh
bash .github/scripts/shellcheck-all.sh            # pinned 0.10.0, as ci.yml installs
bash .github/scripts/actionlint-all.sh
bash .github/scripts/self-ref-check.sh
bash .github/scripts/marker-check.sh
bash .github/scripts/vendored-check.sh
bash actions/changelog-armed/changelog-armed.sh
```

and run the suite once under the runner's `jq` as well as your own.

### Every branch that was open during the sync is now stale

Forgejo tests branch heads; it never tests what two branches produce together,
and it never re-tests an open PR when `main` moves under it. So after a sync
lands, **every PR that was open across it is green against a tree that no
longer exists** — its run did not contain the test files and rules the sync
introduced.

Both halves of that bit in this sync:

- `#206` and `#207` were cut from the pre-sync base. Their green suites had 22
  test files; the merged tree has 28.
- `#206`'s changelog fragment was individually green and made the **combined**
  tree red, because the terminal-citation rule (#262) arrives *with* the sync
  and the fragment was written against a base without it.

So, for each PR still open:

```sh
git merge origin/main            # in the branch — do not rewrite its commits
CEREMONY_REQUIRE_NPM=1 CEREMONY_REQUIRE_YQ=1 bash test/run.sh
```

or, if you are only checking rather than updating, merge them into a scratch
worktree together and run the full current suite and static guards there. A
prior approval is evidence about the tree it was given on; after a sync it is
not evidence about the tree the operator would merge.

### 8. After it merges — audit by executed steps, never by colour

The sync issue uses `Refs`, not `Closes`, and stays open until a real sweep on
the merged `main` is linked to it.

**A green run is not that evidence.** In this sync the first post-merge run was
green and had reconciled *nothing*: upstream's #209 restructure moved reconcile
out of the labels caller and behind a dispatch this forge cannot perform, so
the only job that ran was the refusal. Green, correct, and proof of the
refusal path only.

So before citing any run:

1. **Inventory what the sync changed about workflow triggers and jobs** — which
   jobs exist now, which events fire them, and which of those this forge can
   actually serve. A restructure upstream can move work between workflows
   without touching a line of the code that does it.
2. **Read the run's executed steps**, not its status. Name the job that did the
   thing, and quote the line that shows it did.
3. A green *skipped-or-refusing* path is valid evidence **for that path**, and
   never evidence that the work happened.

Neither of these is caught by the no-runtime-`gh` scan in step 4: in this sync
both failures occurred with that guard green and CI green.

## Where the forge delta lives

Forge-specific behaviour is confined to the files below. Keeping it there is
what makes each sync cost 18 hunks instead of hundreds, and
`test/upstream-delta.test.sh` fails the PR that scatters it into a new file.

| file | what is forge-specific about it |
|---|---|
| `lib/forge.sh` | the selector: `forge_detect`, `forge_client`, `forge_preflight` |
| `lib/forge-github.sh` | the gh backend — the one file allowed to speak `gh` |
| `lib/forge-forgejo.sh` | the Forgejo backend, `/api/v1` over curl + jq |
| `lib/closes_references.sh` | the closing-keyword parser that replaced GraphQL |
| `.github/labels.conf` | this instance's roster |
| `drills/` | records of runs on this instance |

If a sync needs forge branching somewhere else, that is a design decision, not
a detail: add the file to the inventory in the same PR, with the reason.