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`lab` and the public `dev` line share only the repository's first commit as a merge base, so `git log lab..dev` lists two thousand commits that are almost all already present on both sides under different SHAs. Nothing in that output says which public fixes never reached `lab`, which is the only question that matters before `lab` becomes a release. `scripts/ref_parity_audit.py` samples the most distinctive added lines from each commit in the range and searches the other tree for them with `git grep -F`, then reports the file-level presence diff. The two complement each other: a commit whose probes are all found while one of the files it added is missing from the target is a fix whose production change was reproduced without its test, which the line sampling alone cannot see. Probes are stripped of indentation and searched for anywhere in the tree, so a port that moved or was re-indented still reads as present. Verdicts are absent / partial / present / no-probe, and the report says outright that the commit verdicts are a heuristic while the two file lists are exact. Read-only by construction: `git log`, `show`, `diff`, `grep`, `ls-tree` and `merge-base` only, no remote access, and it does not import the app package.
90 lines
4.4 KiB
Markdown
90 lines
4.4 KiB
Markdown
# Ref parity audit
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`scripts/ref_parity_audit.py` reports which commits on one git ref left no trace
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in another, and which files exist on one and not the other. It is read-only: it
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runs `git log`, `git show`, `git diff`, `git grep`, `git ls-tree` and
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`git merge-base`, writes nothing to the repository, touches no remote, and does
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not import the application package.
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## Why it exists
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`lab` and the public `dev` line share only the repository's first commit as a
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merge base, so `git log lab..dev` lists thousands of commits — nearly all of
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which are in fact present on both sides, having arrived under different SHAs. A
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plain log tells you nothing about what is actually missing.
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The question that matters before `lab` becomes a release is narrower: is there a
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fix on the public line that never reached `lab`? This script answers that by
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sampling distinctive added lines from each commit and searching the other tree
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for them.
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## Running it
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```bash
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git remote add public https://github.com/odysseus-dev/odysseus.git # once
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git fetch public dev --no-tags
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scripts/ref_parity_audit.py --source public/dev --target lab --since 2026-08-10
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```
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Roughly 30 seconds for a 100-commit window; it grows linearly, so bound a wide
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audit with `--since`. Add `--format json` for a machine-readable report and
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`--output PATH` to write it to a file.
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| Flag | Effect |
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| `--source REF` | The ref whose commits are audited. Required. |
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| `--target REF` | The ref searched for traces of them. Required. |
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| `--since` / `--until` | Bound the commit range. Both filter **committer** date, which is also the date the report prints. |
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| `--traversal linear` | Default. Individual authored commits, merges dropped. Finds a fix that arrived on a side branch. |
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| `--traversal first-parent` | One row per merge into the source branch, which reads as one row per merged pull request. |
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| `--probes N` | Probe lines sampled per commit, default 4. |
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| `--exclude GLOB` | Extra path glob whose lines are not used as probes. Repeatable. |
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| `--no-default-excludes` | Drop the built-in vendored / lockfile / binary exclusions. |
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| `--top N` | Rows shown per file list, default 50. |
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| `--repo PATH` | Repository to run in. Defaults to this checkout. |
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## How a verdict is reached
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For each commit in `target..source`, the script takes the patch with no context
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lines, collects the added lines, drops the ones from vendored code, committed
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build output, lockfiles and binaries, and keeps those that are at least 24
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characters long and name at least two distinct identifiers. It ranks what is
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left by how many distinct identifiers each line carries (length breaks ties),
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takes the top `--probes`, and searches the whole target tree for each one with
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`git grep --fixed-strings`.
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Probes are stripped of leading and trailing whitespace, so a change that was
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re-indented on the target still counts as present. The whole target tree is
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searched, not the same file, because a ported fix routinely moves.
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| Verdict | Meaning |
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| **absent** | No probe found anywhere in the target. Treat as a real gap and read the diff. |
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| **partial** | Some probes found. **Inconclusive.** A line can be rewritten by a refactor on the target and still be the same change. |
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| **present** | Every probe found. The change is almost certainly there in some form. |
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| **no-probe** | Nothing to sample: a deletion-only commit, or one touching only excluded paths. No verdict. |
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## What is exact and what is a heuristic
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**Exact:** the two file-presence lists. They come from `git ls-tree` on both
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refs, so a file in "on the source and not the target" is definitely not there.
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**Heuristic:** every commit verdict. It samples at most four lines out of a
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diff that may be hundreds, and a probe can be absent because the area was
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refactored rather than because the change was never made.
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The two complement each other in a specific and useful way. A commit that reads
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**present** while one of the files it added shows up in the source-only list is
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almost always a fix whose production change was reproduced on the target without
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its test. The line sampling cannot see that; the presence diff can.
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Read the diff before porting anything. The verdicts say where to look, not what
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to do.
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## Tests
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`tests/test_ref_parity_audit.py`. The end-to-end cases build a throwaway
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repository with two branches off one root, so the verdicts come from git's own
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`grep` and `diff` rather than from a fake.
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