Teach builtin_diffstat() to consult the hunk provider interface through
diff_provider_consult(), new here: the consult-only entry that answers
without loading content or computing, so it never returns
DIFF_PROVIDER_ERROR. On an answer, the summing callback accumulates the
provided counts directly into the diffstat entry; the blobs were already
loaded for the binary check, so an answer saves the diff run, not the
content load (blame, taught next, skips its loads too). On an
unanswered outcome it computes as before and, with a writer attached,
records what it computed; on unanswered-no-record it computes without
recording.
The provider behind the consult is the diff-hunks store, registered in
front of the terminal builtin computation. Its consult serves a
recorded pair through diff_hunks_replay(), which validates the sequence
before any hunk reaches the callback, so direct accumulation is safe.
The request gains the pair's object ids and the diff options read by the
exclusions below. A side whose bytes are not a stored blob, such as a
working-tree file or a gitlink, has a NULL id; the store passes it by and
the terminal provider computes it. diff_provider_emit_hunks() walks the
same chain, so blame's requests follow these rules the moment blame
supplies identity. The walk also insists, as a BUG check, that a
request's diff options belong to the repository whose chain it walks.
Each exclusion lives with the provider whose key cannot express it. -I
patterns and --anchored shape the diff outside the store key, and break
detection (-B) rescores the pair outside it; the store's consult maps
all three to stop-no-record, so such a request is neither served nor
recorded for any consumer. The consumer-side guard the recording commit
carried for those three comes out here. The compile-time assert on
xpparam_t's layout sits next to that decision, forcing an explicit
keying decision whenever a diff parameter is added. The stat consumer
keeps only the exclusion that is not about the key: --ignore-blank-lines
is part of the key but coalesces hunks differently between the
text-emitting and coordinate-callback paths, so the consumer returns
before consulting. A "log -L" range-scoped stat neither reads nor
records; the line-range filter computes it as before.
"git diff", "git log", "git show", and "git diff-tree" with the --stat,
--numstat, and --shortstat formats consult the interface. Reading is
controlled by core.diffHunks.
An answer is invisible in the output, so the store counts the pairs it
serves and the consultations it cannot, and diff_hunks_read_stats()
reports both; the stat path emits the hits as a trace2 "read-hits" datum
for tests and tuning. The counters live on the store because only the
store knows whether a consultation reached it, and none of its exclusion
legs reaches the replay, so none counts as a miss.
Extend t4220 with the read half:
- output parity with and without the store, at several context lengths
and both directions, and reversed pairs keying apart;
- the consultation made visible through the read-hits datum, and the
trim-divergent pair correct at every context;
- the settings that must bypass the store doing so in both directions
(-I, -B, --anchored, --ignore-blank-lines), asserted through the trace
rather than output parity alone, which a coincidentally equal count
could satisfy;
- a driver-forced algorithm keying apart rather than bypassing: it is
part of the key, so a read under it misses the default entries and a
warm records under its own.
A "log -L" range-scoped stat neither reads nor records.
Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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