Before diffing a target blob against a parent, offer the pair's identity
to the hunk provider interface. Blame's requests have gone through
diff_provider_emit_hunks() since the interface arrived, but carried no
identity, so nothing could answer them. Now blame fills in the pair's
blob object ids and its diff options, and the chain serves the pair from
the store, keyed by the ids and the request's xdiff flags, before the
terminal provider falls back to fill-and-compute. Blame diffs at zero
context, which is not part of the key. An answer replays the recorded
hunks through blame_chunk_cb without loading either blob; a request
carrying -I patterns or anchors is outside the key and always computes.
Blame withholds the identity where its diff is not the plain blob-pair
diff the key describes: reverse blame, ignored revisions, textconv
paths, and the working-tree or --contents pseudo-commit, whose blob is
not a stored object. Those requests always compute. Whitespace and
algorithm options such as -w instead change blame's xdl_opts, so the
consult keys a different entry and misses a store warmed without them.
Blame's default xdl_opts now come from DIFF_HUNKS_DEFAULT_XDL_OPTS, new
here, which records the key-relevant defaults a diff_options-based
consumer already carries (today the indent heuristic), so a default
blame run and a default "log --stat" warming run share keys by
construction.
"--show-stats" reports how many pairs the store served and how many
consultations it could not, read from diff_hunks_read_stats(); the store
counts its own consultations, so blame keeps no tally.
Extend t4220 with the blame side:
- parity for plain, --porcelain, and --incremental output, and hit and
miss accounting across warming runs;
- the blame inputs that must bypass or miss the store: -w, indent
heuristics, --reverse, textconv, -M/-C, and the --ignore-rev pass;
- rename and merge handling, and --contents;
- reading a truncated or corrupt store as absent, and a crafted
zero-hunk record as a miss that verify flags.
Add p4218, measuring the cost of a warming run and the read speedups.
Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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