From 38f88051dae6ddb2f1cdb9c7415d4ba6caef04af Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ren=C3=A9=20Scharfe?= Date: Sun, 30 Nov 2025 12:47:17 +0100 Subject: [PATCH] diff-index: don't queue unchanged filepairs with diff_change() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit diff_cache() queues unchanged filepairs if the flag find_copies_harder is set, and uses diff_change() for that. This function allocates a filespec for each side, does a few other things that are unnecessary for unchanged filepairs and always sets the diff_flag has_changes, which is simply misleading in this case. Add a new streamlined function for queuing unchanged filepairs and use it in show_modified(), which is called by diff_cache() via oneway_diff() and do_oneway_diff(). It allocates only a single filespec for each filepair and uses it twice with reference counting. This has a measurable effect if there are a lot of them, like in the Linux repo: Benchmark 1: ./git_v2.52.0 -C ../linux diff --cached --find-copies-harder Time (mean ± σ): 31.8 ms ± 0.2 ms [User: 24.2 ms, System: 6.3 ms] Range (min … max): 31.5 ms … 32.3 ms 85 runs Benchmark 2: ./git -C ../linux diff --cached --find-copies-harder Time (mean ± σ): 23.9 ms ± 0.2 ms [User: 18.1 ms, System: 4.6 ms] Range (min … max): 23.5 ms … 24.4 ms 111 runs Summary ./git -C ../linux diff --cached --find-copies-harder ran 1.33 ± 0.01 times faster than ./git_v2.52.0 -C ../linux diff --cached --find-copies-harder Signed-off-by: René Scharfe Signed-off-by: Junio C Hamano --- diff-lib.c | 13 ++++++------- diff.c | 20 ++++++++++++++++++++ diff.h | 5 +++++ 3 files changed, 31 insertions(+), 7 deletions(-) diff --git a/diff-lib.c b/diff-lib.c index b8f8f3bc31..8e624f38c6 100644 --- a/diff-lib.c +++ b/diff-lib.c @@ -418,13 +418,12 @@ static int show_modified(struct rev_info *revs, } oldmode = old_entry->ce_mode; - if (mode == oldmode && oideq(oid, &old_entry->oid) && !dirty_submodule && - !revs->diffopt.flags.find_copies_harder) - return 0; - - diff_change(&revs->diffopt, oldmode, mode, - &old_entry->oid, oid, 1, !is_null_oid(oid), - old_entry->name, 0, dirty_submodule); + if (mode != oldmode || !oideq(oid, &old_entry->oid) || dirty_submodule) + diff_change(&revs->diffopt, oldmode, mode, + &old_entry->oid, oid, 1, !is_null_oid(oid), + old_entry->name, 0, dirty_submodule); + else if (revs->diffopt.flags.find_copies_harder) + diff_same(&revs->diffopt, mode, oid, old_entry->name); return 0; } diff --git a/diff.c b/diff.c index a1961526c0..c3063d827e 100644 --- a/diff.c +++ b/diff.c @@ -7347,6 +7347,26 @@ void diff_change(struct diff_options *options, concatpath, old_dirty_submodule, new_dirty_submodule); } +void diff_same(struct diff_options *options, + unsigned mode, + const struct object_id *oid, + const char *concatpath) +{ + struct diff_filespec *one; + + if (S_ISGITLINK(mode) && is_submodule_ignored(concatpath, options)) + return; + + if (options->prefix && + strncmp(concatpath, options->prefix, options->prefix_length)) + return; + + one = alloc_filespec(concatpath); + fill_filespec(one, oid, 1, mode); + one->count++; + diff_queue(&diff_queued_diff, one, one); +} + struct diff_filepair *diff_unmerge(struct diff_options *options, const char *path) { struct diff_filepair *pair; diff --git a/diff.h b/diff.h index 31eedd5c0c..e80503aebb 100644 --- a/diff.h +++ b/diff.h @@ -572,6 +572,11 @@ void diff_change(struct diff_options *, const char *fullpath, unsigned dirty_submodule1, unsigned dirty_submodule2); +void diff_same(struct diff_options *, + unsigned mode, + const struct object_id *oid, + const char *fullpath); + struct diff_filepair *diff_unmerge(struct diff_options *, const char *path); void compute_diffstat(struct diff_options *options, struct diffstat_t *diffstat,