# zit 0.3.19

zit 0.3.19 takes most of a second off `zit log` on a large repository. The
cost was not cold open, which was the standing suspicion: it was `log`
opening the repository in the mode meant for write verbs, and doing it twice.
A warm `log` on a million-artifact store now returns its first row in about a
tenth of a second, and on a hundred-thousand-artifact store in about a
fiftieth.

No artifact, tag namespace, sync message, or on-disk repository format changed.

## `log` opens on the zero-parse image

A warm cache hit reads exactly one sidecar, the repository image, and points
at it in place. What the open does after the bytes land depends on the mode
the verb asks for. Read verbs ask for the image and get a view in the time it
takes to checksum it. Write verbs ask for the full derive, which replays
every record out of the image into a mutable state, because an image is
read-only by construction.

`log` reached past the open funnel every other read verb goes through and
called the repository open with a default options struct. The default was the
full replay. For a symbolic name such as `trunk` it did so twice: once to
resolve the name, once to walk. Nothing failed, output was correct, and every
`log` paid two write-verb opens for a read.

`log` now opens once, on the image path, shared by name resolution, the PATH
route and the default listing. A bare `--long` listing of a literal ID, which
needs no view at all, skips the open entirely. Output is byte-identical on
every route.

| release build, warm page cache | 0.3.18 | 0.3.19 |
|---|---|---|
| `log -n 1 trunk`, SQLite mirror (131,558 artifacts) | 0.46s | 0.02s |
| `log -n 1 trunk`, pkgsrc sub-manifest mirror (1,249,347 artifacts) | 0.94s | 0.05–0.10s |
| `log --long -n 3 trunk src/btree.c`, SQLite mirror | 0.48s | 0.07s |
| `log --long -n 5 trunk Makefile`, pkgsrc sub-manifest mirror | 1.32s | 0.40s |

What remains on the pkgsrc per-file query is after open: the manifest reads
`--long` needs for its rows, and the index lookup.

## The open mode is no longer defaulted

The trap that made this a bug rather than a design was a defaulted field: a
verb that opened the repository directly and said nothing about mode got the
full replay silently. The same trap caught `diff` in an earlier release. The
field has no default now; every direct caller declares the mode it wants, so
the next verb written past the funnel cannot inherit the expensive one
without saying so. Every existing caller other than `log` declares the mode
it already had, so nothing else changed behaviour.

An end-to-end test runs every `log` route on a flat store and a tree store
under the derive-footprint seam and fails if any of them replays a record.

## Compatibility

- No on-disk repository or wire format changed; Fossil RFC revision 00 remains
  the target.
- No command, flag, or output changed. `ZIT_DERIVE_FOOTPRINT` remains a
  diagnostic seam.

## Qualification

`zig build test`, `e2e`, `smoke` (Fossil interop against a real `fossil`),
`muscle`, `git-import-e2e`, `git-export-e2e`, `dst`, and `cross`, plus the
three-runner CI battery. The timings are release builds against the mirrors
in the benchmark corpus, warm cache, both columns run alone on the same
machine, with each route's output compared byte for byte between the two
builds.