From 188e9e28c5287f3f160b5f14e3e551b1c55c7301 Mon Sep 17 00:00:00 2001
From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Mon, 12 Apr 2021 19:15:14 +0200
Subject: pickaxe: die when -G and --pickaxe-regex are combined
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

When the -G and --pickaxe-regex options are combined we simply ignore
the --pickaxe-regex option. Let's die instead as suggested by our
documentation, since -G is always a regex.

When --pickaxe-regex was added in d01d8c6782 (Support for pickaxe
matching regular expressions, 2006-03-29) only the -S option
existed. Then when -G was added in f506b8e8b5 (git log/diff: add
-G<regexp> that greps in the patch text, 2010-08-23) neither the
documentation for --pickaxe-regex was updated accordingly, nor was
something like this assertion added.

Since 5bc3f0b567 (diffcore-pickaxe doc: document -S and -G properly,
2013-05-31) we've claimed that --pickaxe-regex should only be used
with -S, but have silently tolerated combining it with -G, let's die
instead.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 diff.c | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'diff.c')

diff --git a/diff.c b/diff.c
index 4acccd9d7e..f9e86bca04 100644
--- a/diff.c
+++ b/diff.c
@@ -4628,6 +4628,9 @@ void diff_setup_done(struct diff_options *options)
 	if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_MASK))
 		die(_("-G, -S and --find-object are mutually exclusive"));
 
+	if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_G_REGEX_MASK))
+		die(_("-G and --pickaxe-regex are mutually exclusive, use --pickaxe-regex with -S"));
+
 	/*
 	 * Most of the time we can say "there are changes"
 	 * only by checking if there are changed paths, but
-- 
cgit 1.2.3-korg


From d26ec8800969ea1b692e0c87100dc4235cfa12e2 Mon Sep 17 00:00:00 2001
From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Mon, 12 Apr 2021 19:15:15 +0200
Subject: pickaxe: die when --find-object and --pickaxe-all are combined
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Neither the --pickaxe-all documentation nor --find-object's has ever
suggested that you can combine the two. See f506b8e8b5 (git log/diff:
add -G<regexp> that greps in the patch text, 2010-08-23) and
15af58c1ad (diffcore: add a pickaxe option to find a specific blob,
2018-01-04).

But we've silently tolerated it, which makes the logic in
diffcore_pickaxe() harder to reason about. Let's assert that we won't
have the two combined.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 diff.c                 | 3 +++
 diff.h                 | 2 ++
 t/t4209-log-pickaxe.sh | 3 +++
 3 files changed, 8 insertions(+)

(limited to 'diff.c')

diff --git a/diff.c b/diff.c
index f9e86bca04..c1f47a7f01 100644
--- a/diff.c
+++ b/diff.c
@@ -4631,6 +4631,9 @@ void diff_setup_done(struct diff_options *options)
 	if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_G_REGEX_MASK))
 		die(_("-G and --pickaxe-regex are mutually exclusive, use --pickaxe-regex with -S"));
 
+	if (HAS_MULTI_BITS(options->pickaxe_opts & DIFF_PICKAXE_KINDS_ALL_OBJFIND_MASK))
+		die(_("---pickaxe-all and --find-object are mutually exclusive, use --pickaxe-all with -G and -S"));
+
 	/*
 	 * Most of the time we can say "there are changes"
 	 * only by checking if there are changed paths, but
diff --git a/diff.h b/diff.h
index 5e110d349b..82254396f9 100644
--- a/diff.h
+++ b/diff.h
@@ -558,6 +558,8 @@ int git_config_rename(const char *var, const char *value);
 				 DIFF_PICKAXE_KIND_OBJFIND)
 #define DIFF_PICKAXE_KINDS_G_REGEX_MASK (DIFF_PICKAXE_KIND_G | \
 					 DIFF_PICKAXE_REGEX)
+#define DIFF_PICKAXE_KINDS_ALL_OBJFIND_MASK (DIFF_PICKAXE_ALL | \
+					     DIFF_PICKAXE_KIND_OBJFIND)
 
 #define DIFF_PICKAXE_IGNORE_CASE	32
 
diff --git a/t/t4209-log-pickaxe.sh b/t/t4209-log-pickaxe.sh
index 772c6c1a7c..16166ffd3e 100755
--- a/t/t4209-log-pickaxe.sh
+++ b/t/t4209-log-pickaxe.sh
@@ -63,6 +63,9 @@ test_expect_success 'usage' '
 	grep "mutually exclusive" err &&
 
 	test_expect_code 128 git log -Sstring --find-object=HEAD 2>err &&
+	grep "mutually exclusive" err &&
+
+	test_expect_code 128 git log --pickaxe-all --find-object=HEAD 2>err &&
 	grep "mutually exclusive" err
 '
 
-- 
cgit 1.2.3-korg


From a8d5eb6dc0d61625667b0d8155c425d3629baa12 Mon Sep 17 00:00:00 2001
From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Mon, 12 Apr 2021 19:15:24 +0200
Subject: xdiff-interface: prepare for allowing early return
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Change the function prototype of xdiff_emit_line_fn to return an "int"
instead of "void". Change all of those functions to "return 0",
nothing checks those return values yet, and no behavior is being
changed.

In subsequent commits the interface will be changed to allow early
return via this new return value.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 combine-diff.c     |  5 +++--
 diff.c             | 26 +++++++++++++++-----------
 diffcore-pickaxe.c |  7 ++++---
 range-diff.c       |  3 ++-
 xdiff-interface.c  |  3 ++-
 xdiff-interface.h  |  2 +-
 6 files changed, 27 insertions(+), 19 deletions(-)

(limited to 'diff.c')

diff --git a/combine-diff.c b/combine-diff.c
index 06635f91bc..a12d3bc0d9 100644
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -403,11 +403,11 @@ static void consume_hunk(void *state_,
 	state->sline[state->nb-1].p_lno[state->n] = state->ob;
 }
 
-static void consume_line(void *state_, char *line, unsigned long len)
+static int consume_line(void *state_, char *line, unsigned long len)
 {
 	struct combine_diff_state *state = state_;
 	if (!state->lost_bucket)
-		return; /* not in any hunk yet */
+		return 0; /* not in any hunk yet */
 	switch (line[0]) {
 	case '-':
 		append_lost(state->lost_bucket, state->n, line+1, len-1);
@@ -417,6 +417,7 @@ static void consume_line(void *state_, char *line, unsigned long len)
 		state->lno++;
 		break;
 	}
+	return 0;
 }
 
 static void combine_diff(struct repository *r,
diff --git a/diff.c b/diff.c
index c1f47a7f01..7a03c581c7 100644
--- a/diff.c
+++ b/diff.c
@@ -2336,7 +2336,7 @@ static void find_lno(const char *line, struct emit_callback *ecbdata)
 	ecbdata->lno_in_postimage = strtol(p + 1, NULL, 10);
 }
 
-static void fn_out_consume(void *priv, char *line, unsigned long len)
+static int fn_out_consume(void *priv, char *line, unsigned long len)
 {
 	struct emit_callback *ecbdata = priv;
 	struct diff_options *o = ecbdata->opt;
@@ -2372,7 +2372,7 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 		len = sane_truncate_line(line, len);
 		find_lno(line, ecbdata);
 		emit_hunk_header(ecbdata, line, len);
-		return;
+		return 0;
 	}
 
 	if (ecbdata->diff_words) {
@@ -2382,11 +2382,11 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 		if (line[0] == '-') {
 			diff_words_append(line, len,
 					  &ecbdata->diff_words->minus);
-			return;
+			return 0;
 		} else if (line[0] == '+') {
 			diff_words_append(line, len,
 					  &ecbdata->diff_words->plus);
-			return;
+			return 0;
 		} else if (starts_with(line, "\\ ")) {
 			/*
 			 * Eat the "no newline at eof" marker as if we
@@ -2395,11 +2395,11 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 			 * defer processing. If this is the end of
 			 * preimage, more "+" lines may come after it.
 			 */
-			return;
+			return 0;
 		}
 		diff_words_flush(ecbdata);
 		emit_diff_symbol(o, s, line, len, 0);
-		return;
+		return 0;
 	}
 
 	switch (line[0]) {
@@ -2423,6 +2423,7 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 				 line, len, 0);
 		break;
 	}
+	return 0;
 }
 
 static void pprint_rename(struct strbuf *name, const char *a, const char *b)
@@ -2522,7 +2523,7 @@ static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
 	return x;
 }
 
-static void diffstat_consume(void *priv, char *line, unsigned long len)
+static int diffstat_consume(void *priv, char *line, unsigned long len)
 {
 	struct diffstat_t *diffstat = priv;
 	struct diffstat_file *x = diffstat->files[diffstat->nr - 1];
@@ -2531,6 +2532,7 @@ static void diffstat_consume(void *priv, char *line, unsigned long len)
 		x->added++;
 	else if (line[0] == '-')
 		x->deleted++;
+	return 0;
 }
 
 const char mime_boundary_leader[] = "------------";
@@ -3208,7 +3210,7 @@ static void checkdiff_consume_hunk(void *priv,
 	data->lineno = nb - 1;
 }
 
-static void checkdiff_consume(void *priv, char *line, unsigned long len)
+static int checkdiff_consume(void *priv, char *line, unsigned long len)
 {
 	struct checkdiff_t *data = priv;
 	int marker_size = data->conflict_marker_size;
@@ -3232,7 +3234,7 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 		}
 		bad = ws_check(line + 1, len - 1, data->ws_rule);
 		if (!bad)
-			return;
+			return 0;
 		data->status |= bad;
 		err = whitespace_error_string(bad);
 		fprintf(data->o->file, "%s%s:%d: %s.\n",
@@ -3244,6 +3246,7 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 	} else if (line[0] == ' ') {
 		data->lineno++;
 	}
+	return 0;
 }
 
 static unsigned char *deflate_it(char *data,
@@ -6121,17 +6124,18 @@ void flush_one_hunk(struct object_id *result, git_hash_ctx *ctx)
 	}
 }
 
-static void patch_id_consume(void *priv, char *line, unsigned long len)
+static int patch_id_consume(void *priv, char *line, unsigned long len)
 {
 	struct patch_id_t *data = priv;
 	int new_len;
 
 	if (len > 12 && starts_with(line, "\\ "))
-		return;
+		return 0;
 	new_len = remove_space(line, len);
 
 	the_hash_algo->update_fn(data->ctx, line, new_len);
 	data->patchlen += new_len;
+	return 0;
 }
 
 static void patch_id_add_string(git_hash_ctx *ctx, const char *str)
diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index b7494fdf89..27aa20be35 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -19,21 +19,22 @@ struct diffgrep_cb {
 	int hit;
 };
 
-static void diffgrep_consume(void *priv, char *line, unsigned long len)
+static int diffgrep_consume(void *priv, char *line, unsigned long len)
 {
 	struct diffgrep_cb *data = priv;
 	regmatch_t regmatch;
 
 	if (line[0] != '+' && line[0] != '-')
-		return;
+		return 0;
 	if (data->hit)
 		/*
 		 * NEEDSWORK: we should have a way to terminate the
 		 * caller early.
 		 */
-		return;
+		return 0;
 	data->hit = !regexec_buf(data->regexp, line + 1, len - 1, 1,
 				 &regmatch, 0);
+	return 0;
 }
 
 static int diff_grep(mmfile_t *one, mmfile_t *two,
diff --git a/range-diff.c b/range-diff.c
index 116fb0735c..83c90f946e 100644
--- a/range-diff.c
+++ b/range-diff.c
@@ -274,9 +274,10 @@ static void find_exact_matches(struct string_list *a, struct string_list *b)
 	hashmap_clear(&map);
 }
 
-static void diffsize_consume(void *data, char *line, unsigned long len)
+static int diffsize_consume(void *data, char *line, unsigned long len)
 {
 	(*(int *)data)++;
+	return 0;
 }
 
 static void diffsize_hunk(void *data, long ob, long on, long nb, long nn,
diff --git a/xdiff-interface.c b/xdiff-interface.c
index 4d20069302..5d8c8c67dc 100644
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -31,7 +31,7 @@ static int xdiff_out_hunk(void *priv_,
 	return 0;
 }
 
-static void consume_one(void *priv_, char *s, unsigned long size)
+static int consume_one(void *priv_, char *s, unsigned long size)
 {
 	struct xdiff_emit_state *priv = priv_;
 	char *ep;
@@ -43,6 +43,7 @@ static void consume_one(void *priv_, char *s, unsigned long size)
 		size -= this_size;
 		s += this_size;
 	}
+	return 0;
 }
 
 static int xdiff_outf(void *priv_, mmbuffer_t *mb, int nbuf)
diff --git a/xdiff-interface.h b/xdiff-interface.h
index 93df26900c..0198f9632f 100644
--- a/xdiff-interface.h
+++ b/xdiff-interface.h
@@ -11,7 +11,7 @@
  */
 #define MAX_XDIFF_SIZE (1024UL * 1024 * 1023)
 
-typedef void (*xdiff_emit_line_fn)(void *, char *, unsigned long);
+typedef int (*xdiff_emit_line_fn)(void *, char *, unsigned long);
 typedef void (*xdiff_emit_hunk_fn)(void *data,
 				   long old_begin, long old_nr,
 				   long new_begin, long new_nr,
-- 
cgit 1.2.3-korg


From 5d93460024541909337d6b08a8bec10b71caaf73 Mon Sep 17 00:00:00 2001
From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Mon, 12 Apr 2021 19:15:29 +0200
Subject: xdiff-interface: replace discard_hunk_line() with a flag
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Remove the dummy discard_hunk_line() function added in
3b40a090fd4 (diff: avoid generating unused hunk header lines,
2018-11-02) in favor of having a new XDL_EMIT_NO_HUNK_HDR flag, for
use along with the two existing and similar XDL_EMIT_* flags.

Unlike the recently amended xdiff_emit_line_fn interface which'll be
called in a loop in xdl_emit_diff(), the hunk header is only emitted
once.

It makes more sense to pass this as a flag than provide a dummy
callback because that function may be able to skip doing certain work
if it knows the caller is doing nothing with the hunk header.

It would be possible to do so in the case of -U0 now, but the benefit
of doing so is so small that I haven't bothered. But this leaves the
door open to that, and more importantly makes the API use more
intuitive.

The reason we're putting a flag in the gap between 1<<0 and 1<<2 is
that the old 1<<1 flag was removed in 907681e940d (xdiff: drop
XDL_EMIT_COMMON, 2016-02-23) without re-ordering the remaining flags.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 diff.c             | 7 ++++---
 diffcore-pickaxe.c | 3 ++-
 xdiff-interface.c  | 6 ------
 xdiff-interface.h  | 8 --------
 xdiff/xdiff.h      | 1 +
 xdiff/xemit.c      | 3 ++-
 6 files changed, 9 insertions(+), 19 deletions(-)

(limited to 'diff.c')

diff --git a/diff.c b/diff.c
index 7a03c581c7..fe3abac79f 100644
--- a/diff.c
+++ b/diff.c
@@ -3725,7 +3725,8 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 		xpp.anchors_nr = o->anchors_nr;
 		xecfg.ctxlen = o->context;
 		xecfg.interhunkctxlen = o->interhunkcontext;
-		if (xdi_diff_outf(&mf1, &mf2, discard_hunk_line,
+		xecfg.flags = XDL_EMIT_NO_HUNK_HDR;
+		if (xdi_diff_outf(&mf1, &mf2, NULL,
 				  diffstat_consume, diffstat, &xpp, &xecfg))
 			die("unable to generate diffstat for %s", one->path);
 
@@ -6233,8 +6234,8 @@ static int diff_get_patch_id(struct diff_options *options, struct object_id *oid
 
 		xpp.flags = 0;
 		xecfg.ctxlen = 3;
-		xecfg.flags = 0;
-		if (xdi_diff_outf(&mf1, &mf2, discard_hunk_line,
+		xecfg.flags = XDL_EMIT_NO_HUNK_HDR;
+		if (xdi_diff_outf(&mf1, &mf2, NULL,
 				  patch_id_consume, &data, &xpp, &xecfg))
 			return error("unable to generate patch-id diff for %s",
 				     p->one->path);
diff --git a/diffcore-pickaxe.c b/diffcore-pickaxe.c
index 96183f4cfa..c88e50c632 100644
--- a/diffcore-pickaxe.c
+++ b/diffcore-pickaxe.c
@@ -53,6 +53,7 @@ static int diff_grep(mmfile_t *one, mmfile_t *two,
 	memset(&xecfg, 0, sizeof(xecfg));
 	ecbdata.regexp = regexp;
 	ecbdata.hit = 0;
+	xecfg.flags = XDL_EMIT_NO_HUNK_HDR;
 	xecfg.ctxlen = o->context;
 	xecfg.interhunkctxlen = o->interhunkcontext;
 
@@ -60,7 +61,7 @@ static int diff_grep(mmfile_t *one, mmfile_t *two,
 	 * An xdiff error might be our "data->hit" from above. See the
 	 * comment for xdiff_emit_line_fn in xdiff-interface.h
 	 */
-	ret = xdi_diff_outf(one, two, discard_hunk_line, diffgrep_consume,
+	ret = xdi_diff_outf(one, two, NULL, diffgrep_consume,
 			    &ecbdata, &xpp, &xecfg);
 	if (ecbdata.hit)
 		return 1;
diff --git a/xdiff-interface.c b/xdiff-interface.c
index 50c0ef759d..95f13a93ff 100644
--- a/xdiff-interface.c
+++ b/xdiff-interface.c
@@ -126,12 +126,6 @@ int xdi_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp, xdemitconf_t co
 	return xdl_diff(&a, &b, xpp, xecfg, xecb);
 }
 
-void discard_hunk_line(void *priv,
-		       long ob, long on, long nb, long nn,
-		       const char *func, long funclen)
-{
-}
-
 int xdi_diff_outf(mmfile_t *mf1, mmfile_t *mf2,
 		  xdiff_emit_hunk_fn hunk_fn,
 		  xdiff_emit_line_fn line_fn,
diff --git a/xdiff-interface.h b/xdiff-interface.h
index 3b6819586d..4301a7eef2 100644
--- a/xdiff-interface.h
+++ b/xdiff-interface.h
@@ -53,14 +53,6 @@ void xdiff_clear_find_func(xdemitconf_t *xecfg);
 int git_xmerge_config(const char *var, const char *value, void *cb);
 extern int git_xmerge_style;
 
-/*
- * Can be used as a no-op hunk_fn for xdi_diff_outf(), since a NULL
- * one just sends the hunk line to the line_fn callback).
- */
-void discard_hunk_line(void *priv,
-		       long ob, long on, long nb, long nn,
-		       const char *func, long funclen);
-
 /*
  * Compare the strings l1 with l2 which are of size s1 and s2 respectively.
  * Returns 1 if the strings are deemed equal, 0 otherwise.
diff --git a/xdiff/xdiff.h b/xdiff/xdiff.h
index 7a04605146..b29deca5de 100644
--- a/xdiff/xdiff.h
+++ b/xdiff/xdiff.h
@@ -50,6 +50,7 @@ extern "C" {
 
 /* xdemitconf_t.flags */
 #define XDL_EMIT_FUNCNAMES (1 << 0)
+#define XDL_EMIT_NO_HUNK_HDR (1 << 1)
 #define XDL_EMIT_FUNCCONTEXT (1 << 2)
 
 /* merge simplification levels */
diff --git a/xdiff/xemit.c b/xdiff/xemit.c
index 9d7d6c5087..1cbf2b9829 100644
--- a/xdiff/xemit.c
+++ b/xdiff/xemit.c
@@ -278,7 +278,8 @@ int xdl_emit_diff(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
 				      s1 - 1, funclineprev);
 			funclineprev = s1 - 1;
 		}
-		if (xdl_emit_hunk_hdr(s1 + 1, e1 - s1, s2 + 1, e2 - s2,
+		if (!(xecfg->flags & XDL_EMIT_NO_HUNK_HDR) &&
+		    xdl_emit_hunk_hdr(s1 + 1, e1 - s1, s2 + 1, e2 - s2,
 				      func_line.buf, func_line.len, ecb) < 0)
 			return -1;
 
-- 
cgit 1.2.3-korg


From 05d2c61c6744212cdef6085832a84b49da77591c Mon Sep 17 00:00:00 2001
From: Elijah Newren <newren@gmail.com>
Date: Thu, 15 Jul 2021 00:45:21 +0000
Subject: diff: correct warning message when renameLimit exceeded

The warning when quadratic rename detection was skipped referred to
"inexact rename detection".  For years, the only linear portion of
rename detection was looking for exact renames, so "inexact rename
detection" was an accurate way to refer to the quadratic portion of
rename detection.  However, that changed with commit bd24aa2f97a0
(diffcore-rename: guide inexact rename detection based on basenames,
2021-02-14).  Let's instead use the term "exhaustive rename detection"
to refer to the quadratic portion.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 diff.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'diff.c')

diff --git a/diff.c b/diff.c
index 52c791574b..2454e34cf6 100644
--- a/diff.c
+++ b/diff.c
@@ -6284,7 +6284,7 @@ static int is_summary_empty(const struct diff_queue_struct *q)
 }
 
 static const char rename_limit_warning[] =
-N_("inexact rename detection was skipped due to too many files.");
+N_("exhaustive rename detection was skipped due to too many files.");
 
 static const char degrade_cc_to_c_warning[] =
 N_("only found copies from modified paths due to too many files.");
-- 
cgit 1.2.3-korg


From 94b82d56866793018a7a9bcbe20c1c061fa41aa8 Mon Sep 17 00:00:00 2001
From: Elijah Newren <newren@gmail.com>
Date: Thu, 15 Jul 2021 00:45:24 +0000
Subject: rename: bump limit defaults yet again

These were last bumped in commit 92c57e5c1d29 (bump rename limit
defaults (again), 2011-02-19), and were bumped both because processors
had gotten faster, and because people were getting ugly merges that
caused problems and reporting it to the mailing list (suggesting that
folks were willing to spend more time waiting).

Since that time:
  * Linus has continued recommending kernel folks to set
    diff.renameLimit=0 (maps to 32767, currently)
  * Folks with repositories with lots of renames were happy to set
    merge.renameLimit above 32767, once the code supported that, to
    get correct cherry-picks
  * Processors have gotten faster
  * It has been discovered that the timing methodology used last time
    probably used too large example files.

The last point is probably worth explaining a bit more:

  * The "average" file size used appears to have been average blob size
    in the linux kernel history at the time (probably v2.6.25 or
    something close to it).
  * Since bigger files are modified more frequently, such a computation
    weights towards larger files.
  * Larger files may be more likely to be modified over time, but are
    not more likely to be renamed -- the mean and median blob size
    within a tree are a bit higher than the mean and median of blob
    sizes in the history leading up to that version for the linux
    kernel.
  * The mean blob size in v2.6.25 was half the average blob size in
    history leading to that point
  * The median blob size in v2.6.25 was about 40% of the mean blob size
    in v2.6.25.
  * Since the mean blob size is more than double the median blob size,
    any file as big as the mean will not be compared to any files of
    median size or less (because they'd be more than 50% dissimilar).
  * Since it is the number of files compared that provides the O(n^2)
    behavior, median-sized files should matter more than mean-sized
    ones.

The combined effect of the above is that the file size used in past
calculations was likely about 5x too large.  Combine that with a CPU
performance improvement of ~30%, and we can increase the limits by
a factor of sqrt(5/(1-.3)) = 2.67, while keeping the original stated
time limits.

Keeping the same approximate time limit probably makes sense for
diff.renameLimit (there is no progress feedback in e.g. git log -p),
but the experience above suggests merge.renameLimit could be extended
significantly.  In fact, it probably would make sense to have an
unlimited default setting for merge.renameLimit, but that would
likely need to be coupled with changes to how progress is displayed.
(See https://lore.kernel.org/git/YOx+Ok%2FEYvLqRMzJ@coredump.intra.peff.net/
for details in that area.)  For now, let's just bump the approximate
time limit from 10s to 1m.

(Note: We do not want to use actual time limits, because getting results
that depend on how loaded your system is that day feels bad, and because
we don't discover that we won't get all the renames until after we've
put in a lot of work rather than just upfront telling the user there are
too many files involved.)

Using the original time limit of 2s for diff.renameLimit, and bumping
merge.renameLimit from 10s to 60s, I found the following timings using
the simple script at the end of this commit message (on an AWS c5.xlarge
which reports as "Intel(R) Xeon(R) Platinum 8124M CPU @ 3.00GHz"):

      N   Timing
   1300    1.995s
   7100   59.973s

So let's round down to nice even numbers and bump the limits from
400->1000, and from 1000->7000.

Here is the measure_rename_perf script (adapted from
https://lore.kernel.org/git/20080211113516.GB6344@coredump.intra.peff.net/
in particular to avoid triggering the linear handling from
basename-guided rename detection):

    #!/bin/bash

    n=$1; shift

    rm -rf repo
    mkdir repo && cd repo
    git init -q -b main

    mkdata() {
      mkdir $1
      for i in `seq 1 $2`; do
        (sed "s/^/$i /" <../sample
         echo tag: $1
        ) >$1/$i
      done
    }

    mkdata initial $n
    git add .
    git commit -q -m initial

    mkdata new $n
    git add .
    cd new
    for i in *; do git mv $i $i.renamed; done
    cd ..
    git rm -q -rf initial
    git commit -q -m new

    time git diff-tree -M -l0 --summary HEAD^ HEAD

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/config/diff.txt  | 2 +-
 Documentation/config/merge.txt | 2 +-
 diff.c                         | 2 +-
 merge-ort.c                    | 2 +-
 merge-recursive.c              | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

(limited to 'diff.c')

diff --git a/Documentation/config/diff.txt b/Documentation/config/diff.txt
index d1b5cfa354..32f84838ac 100644
--- a/Documentation/config/diff.txt
+++ b/Documentation/config/diff.txt
@@ -120,7 +120,7 @@ diff.orderFile::
 diff.renameLimit::
 	The number of files to consider in the exhaustive portion of
 	copy/rename detection; equivalent to the 'git diff' option
-	`-l`.  If not set, the default value is currently 400.  This
+	`-l`.  If not set, the default value is currently 1000.  This
 	setting has no effect if rename detection is turned off.
 
 diff.renames::
diff --git a/Documentation/config/merge.txt b/Documentation/config/merge.txt
index 7cd6d7883b..e27cc63944 100644
--- a/Documentation/config/merge.txt
+++ b/Documentation/config/merge.txt
@@ -37,7 +37,7 @@ merge.renameLimit::
 	rename detection during a merge.  If not specified, defaults
 	to the value of diff.renameLimit.  If neither
 	merge.renameLimit nor diff.renameLimit are specified,
-	currently defaults to 1000.  This setting has no effect if
+	currently defaults to 7000.  This setting has no effect if
 	rename detection is turned off.
 
 merge.renames::
diff --git a/diff.c b/diff.c
index 2454e34cf6..0244a371d3 100644
--- a/diff.c
+++ b/diff.c
@@ -35,7 +35,7 @@
 
 static int diff_detect_rename_default;
 static int diff_indent_heuristic = 1;
-static int diff_rename_limit_default = 400;
+static int diff_rename_limit_default = 1000;
 static int diff_suppress_blank_empty;
 static int diff_use_color_default = -1;
 static int diff_color_moved_default;
diff --git a/merge-ort.c b/merge-ort.c
index b954f7184a..8a84375e94 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -2558,7 +2558,7 @@ static void detect_regular_renames(struct merge_options *opt,
 	diff_opts.detect_rename = DIFF_DETECT_RENAME;
 	diff_opts.rename_limit = opt->rename_limit;
 	if (opt->rename_limit <= 0)
-		diff_opts.rename_limit = 1000;
+		diff_opts.rename_limit = 7000;
 	diff_opts.rename_score = opt->rename_score;
 	diff_opts.show_rename_progress = opt->show_rename_progress;
 	diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
diff --git a/merge-recursive.c b/merge-recursive.c
index 4327e0cfa3..f19f8cc37b 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -1879,7 +1879,7 @@ static struct diff_queue_struct *get_diffpairs(struct merge_options *opt,
 	 */
 	if (opts.detect_rename > DIFF_DETECT_RENAME)
 		opts.detect_rename = DIFF_DETECT_RENAME;
-	opts.rename_limit = (opt->rename_limit >= 0) ? opt->rename_limit : 1000;
+	opts.rename_limit = (opt->rename_limit >= 0) ? opt->rename_limit : 7000;
 	opts.rename_score = opt->rename_score;
 	opts.show_rename_progress = opt->show_rename_progress;
 	opts.output_format = DIFF_FORMAT_NO_OUTPUT;
-- 
cgit 1.2.3-korg