# Selected-path Git maintenance

The optional `git` namespace of `tools/devkit/devkit.py` is a deliberately
narrow maintenance workflow. It is not a replacement for normal Git, the
release executor, required human review, or Gitea's canonical issue state.

From the Meta repository, preview and then save a plan for explicit files:

```sh
python3 tools/devkit/devkit.py git plan --repo core --path webui/src/example.ts --message "Fix the reviewed example"
python3 tools/devkit/devkit.py git plan --repo core --path webui/src/example.ts --message "Fix the reviewed example" --apply
```

Use the saved `git-…` plan ID for the remaining commands. Each mutation needs
its own `--apply`; an unqualified command only previews the operation:

```sh
python3 tools/devkit/devkit.py git commit git-PLAN_ID
python3 tools/devkit/devkit.py git commit git-PLAN_ID --apply
python3 tools/devkit/devkit.py git push git-PLAN_ID
python3 tools/devkit/devkit.py git push git-PLAN_ID --apply
python3 tools/devkit/devkit.py git status git-PLAN_ID
```

The immutable local plan binds the registered repository, HEAD, branch, origin
fetch/push URL hashes, Git configuration, complete index identity, explicit
selected file paths, working-tree hashes, expected Git blobs, and commit message.
Raw remote URLs and file contents are not stored. A changed input blocks the
operation; inspect it and create another plan instead of weakening the check.
Receipts are private local records with integrity checks, not signed approval
or a security attestation.

Commit captures each selected file once, verifies the captured bytes and Git
blob against the plan, and builds an isolated index/tree from the frozen HEAD
plus only those blobs. Git's normal identity rules create the commit object;
an atomic branch compare-and-swap publishes it only if the planned parent is
still current. Active hooks/signing remain refused rather than bypassed.
An editor racing with this operation cannot substitute newer working-tree
bytes: those edits remain uncommitted, and the helper never overwrites files.

The real index is protected by Git's standard index lock. Only selected entries
are updated from a prepared private copy; unrelated staging and index flags are
preserved. If the index changes independently, its new data is not overwritten
and the receipt requires reconciliation. The resulting parent, message,
changed paths, blobs/modes and unrelated index entries are verified.
Git refs and index files are separately atomic, not one filesystem transaction.
Independent writers that ignore the standard index lock can still change refs
during publication. The helper rechecks the exact recorded candidate before
index recovery and before recording success; it refuses an uncertain result
instead of adopting a newer HEAD or claiming that competing work was its own.
Directories, noncanonical paths, implicit globs, staging-all, amend,
force-push and extra-tag publication are not supported. A selected file with
different staged and working-tree changes is refused; decide explicitly which
version to commit using normal Git first.

Push requires the recorded commit to remain current, an unchanged origin and
one standard-transport push destination. It requests a normal, non-forced push
of that commit to the recorded branch and checks the remote branch afterward.
The push preview does not contact a remote. A normal push may run the remote's
usual CI or server-side hooks; this is an external effect of the separately
authorized push, not of planning or committing.

Local active hooks (including index-change hooks), filter/encoding attributes,
signing, external fsmonitor/SSH configuration, Git environment overrides,
in-progress merge/rebase/cherry-pick operations, submodules, symlinks and
assume-unchanged/skip-worktree entries, split indexes and replacement/graft
history are deliberately
unsupported. The helper
refuses these cases instead of disabling hooks, signatures or filters. An
unused globally installed filter definition alone does not block maintenance;
active attributes are checked across tracked files as well as selected files.
Custom remote receive-pack/upload-pack/helper commands, recursive submodule
pushes and partial-clone lazy fetch are also refused. Of inherited `GIT_*`
variables, only `GIT_OPTIONAL_LOCKS`, `GIT_TERMINAL_PROMPT` and `GIT_PAGER` are
allowed (every command explicitly passes `--no-pager`, so the pager is inert);
namespace, identity, alternate-index/object-directory and unknown overrides
are not silently removed. Git subprocesses have bounded input/output and
deadlines; cancellation terminates their owned process group, including
transport helpers. Network failures can still leave a remote effect uncertain,
which is why receipts require explicit reconciliation rather than blind retry.

An interruption or uncertain failure is recorded before any retry. Use
`git reconcile git-PLAN_ID` to preview, then add `--apply` to verify an
already-existing result. Reconciliation never makes a commit or push. It may
finish the selected real-index update after an interrupted commit publication,
but only when the original index fingerprint still matches; independent staged
work is preserved and requires normal Git resolution. For an
uncertain push it may read the frozen remote, but only with `--apply`. If no
planned commit is current, the helper reports that state and requires a fresh
plan after inspection. A forcibly killed process may leave its private scratch
index or an owned Git index lock; the helper never guesses that an existing
lock is safe to delete. Blob/commit preparation can leave unreferenced Git
objects for ordinary Git garbage collection. It never automatically resets,
restores, deletes, or rolls back user work.

The maintenance tests use disposable local repositories and local bare remotes.
They never commit or push the user's workspace repositories.