Merge branch 'en/rename-limits-doc'

gitster · gitster · commit 268055bfdec5 · 2021-07-28T13:18:03.000-07:00
Documentation on "git diff -l&lt;n&gt;" and diff.renameLimit have been
updated, and the defaults for these limits have been raised.

* en/rename-limits-doc:
  rename: bump limit defaults yet again
  diffcore-rename: treat a rename_limit of 0 as unlimited
  doc: clarify documentation for rename/copy limits
  diff: correct warning message when renameLimit exceeded
diff --git a/Documentation/config/diff.txt b/Documentation/config/diff.txt
@@ -118,9 +118,10 @@ diff.orderFile::
 	relative to the top of the working tree.
 
 diff.renameLimit::
-	The number of files to consider when performing the copy/rename
-	detection; equivalent to the 'git diff' option `-l`. This setting
-	has no effect if rename detection is turned off.
+	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 1000.  This
+	setting has no effect if rename detection is turned off.
 
 diff.renames::
 	Whether and how Git detects renames.  If set to "false",
diff --git a/Documentation/config/merge.txt b/Documentation/config/merge.txt
@@ -33,10 +33,12 @@ merge.verifySignatures::
 include::fmt-merge-msg.txt[]
 
 merge.renameLimit::
-	The number of files to consider when performing rename detection
-	during a merge; if not specified, defaults to the value of
-	diff.renameLimit. This setting has no effect if rename detection
-	is turned off.
+	The number of files to consider in the exhaustive portion of
+	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 7000.  This setting has no effect if
+	rename detection is turned off.
 
 merge.renames::
 	Whether Git detects renames.  If set to "false", rename detection
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
@@ -588,11 +588,17 @@ When used together with `-B`, omit also the preimage in the deletion part
 of a delete/create pair.
 
 -l<num>::
-	The `-M` and `-C` options require O(n^2) processing time where n
-	is the number of potential rename/copy targets.  This
-	option prevents rename/copy detection from running if
-	the number of rename/copy targets exceeds the specified
-	number.
+	The `-M` and `-C` options involve some preliminary steps that
+	can detect subsets of renames/copies cheaply, followed by an
+	exhaustive fallback portion that compares all remaining
+	unpaired destinations to all relevant sources.  (For renames,
+	only remaining unpaired sources are relevant; for copies, all
+	original sources are relevant.)  For N sources and
+	destinations, this exhaustive check is O(N^2).  This option
+	prevents the exhaustive portion of rename/copy detection from
+	running if the number of source/destination files involved
+	exceeds the specified number.  Defaults to diff.renameLimit.
+	Note that a value of 0 is treated as unlimited.
 
 ifndef::git-format-patch[]
 --diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]::
diff --git 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;
@@ -6295,7 +6295,7 @@ 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.");
diff --git a/diffcore-rename.c b/diffcore-rename.c
@@ -1091,7 +1091,7 @@ static int too_many_rename_candidates(int num_destinations, int num_sources,
 	 * memory for the matrix anyway.
 	 */
 	if (rename_limit <= 0)
-		rename_limit = 32767;
+		return 0; /* treat as unlimited */
 	if (st_mult(num_destinations, num_sources)
 	    <= st_mult(rename_limit, rename_limit))
 		return 0;
diff --git a/merge-ort.c b/merge-ort.c
@@ -2563,7 +2563,7 @@ 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
@@ -1880,7 +1880,7 @@ 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;
