diff: add renameThreshold configuration option

Documentation/config/diff.adoc

@@ -154,6 +154,13 @@ endif::git-diff[]
 	`-l`.  If not set, the default value is currently 1000.  This
 	setting has no effect if rename detection is turned off.
 
+`diff.renameThreshold`::
+	The minimum similarity threshold for rename detection;
+	equivalent to the `git diff` option `-M`.  The value is a
+	percentage (e.g. `50%`), or a fraction between 0 and 1
+	(e.g. `0.5`).  If not set, the default is 50%.  This setting
+	has no effect if rename detection is turned off.
+
 `diff.renames`::
 	Whether and how Git detects renames.  If set to `false`,
 	rename detection is disabled. If set to `true`, basic rename

Documentation/config/merge.adoc

@@ -47,6 +47,13 @@ include::fmt-merge-msg.adoc[]
 	currently defaults to 7000.  This setting has no effect if
 	rename detection is turned off.
 
+`merge.renameThreshold`::
+	The minimum similarity threshold for rename detection during
+	a merge.  If not specified, defaults to the value of
+	`diff.renameThreshold`.  See `diff.renameThreshold` for the
+	accepted value format.  This setting has no effect if rename
+	detection is turned off.
+
 `merge.renames`::
 	Whether Git detects renames.  If set to `false`, rename detection
 	is disabled. If set to `true`, basic rename detection is enabled.

Documentation/config/status.adoc

@@ -29,6 +29,12 @@ status.renameLimit::
 	in linkgit:git-status[1] and linkgit:git-commit[1]. Defaults to
 	the value of diff.renameLimit.
 
+status.renameThreshold::
+	The minimum similarity threshold for rename detection in
+	linkgit:git-status[1] and linkgit:git-commit[1].  Defaults to
+	the value of diff.renameThreshold.  See `diff.renameThreshold`
+	for the accepted value format.
+
 status.renames::
 	Whether and how Git detects renames in linkgit:git-status[1] and
 	linkgit:git-commit[1] .  If set to "false", rename detection is

builtin/commit.c

@@ -1672,6 +1672,22 @@ static int git_status_config(const char *k, const char *v,
 		s->detect_rename = git_config_rename(k, v);
 		return 0;
 	}
+	if (!strcmp(k, "diff.renamethreshold")) {
+		if (s->rename_score == -1) {
+			const char *arg = v;
+			if (!v)
+				return config_error_nonbool(k);
+			s->rename_score = parse_rename_score(&arg);
+		}
+		return 0;
+	}
+	if (!strcmp(k, "status.renamethreshold")) {
+		const char *arg = v;
+		if (!v)
+			return config_error_nonbool(k);
+		s->rename_score = parse_rename_score(&arg);
+		return 0;
+	}
 	return git_diff_ui_config(k, v, ctx, NULL);
 }
 

diff.c

@@ -56,6 +56,7 @@
 static int diff_detect_rename_default;
 static int diff_indent_heuristic = 1;
 static int diff_rename_limit_default = 1000;
+static int diff_rename_score_default;
 static int diff_suppress_blank_empty;
 static enum git_colorbool diff_use_color_default = GIT_COLOR_UNKNOWN;
 static int diff_color_moved_default;
@@ -398,6 +399,15 @@ int git_diff_ui_config(const char *var, const char *value,
 		diff_detect_rename_default = git_config_rename(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "diff.renamethreshold")) {
+		const char *arg = value;
+		if (!value)
+			return config_error_nonbool(var);
+		diff_rename_score_default = parse_rename_score(&arg);
+		if (*arg)
+			return error(_("invalid value for '%s': '%s'"), var, value);
+		return 0;
+	}
 	if (!strcmp(var, "diff.autorefreshindex")) {
 		diff_auto_refresh_index = git_config_bool(var, value);
 		return 0;
@@ -4856,6 +4866,7 @@ void repo_diff_setup(struct repository *r, struct diff_options *options)
 	options->add_remove = diff_addremove;
 	options->use_color = diff_use_color_default;
 	options->detect_rename = diff_detect_rename_default;
+	options->rename_score = diff_rename_score_default;
 	options->xdl_opts |= diff_algorithm;
 	if (diff_indent_heuristic)
 		DIFF_XDL_SET(options, INDENT_HEURISTIC);

merge-ort.c

@@ -5444,6 +5444,16 @@ static void merge_recursive_config(struct merge_options *opt, int ui)
 	repo_config_get_int(the_repository, "merge.verbosity", &opt->verbosity);
 	repo_config_get_int(the_repository, "diff.renamelimit", &opt->rename_limit);
 	repo_config_get_int(the_repository, "merge.renamelimit", &opt->rename_limit);
+	if (!repo_config_get_string(the_repository, "diff.renamethreshold", &value)) {
+		const char *arg = value;
+		opt->rename_score = parse_rename_score(&arg);
+		free(value);
+	}
+	if (!repo_config_get_string(the_repository, "merge.renamethreshold", &value)) {
+		const char *arg = value;
+		opt->rename_score = parse_rename_score(&arg);
+		free(value);
+	}
 	repo_config_get_bool(the_repository, "merge.renormalize", &renormalize);
 	opt->renormalize = renormalize;
 	if (!repo_config_get_string(the_repository, "diff.renames", &value)) {

t/t4001-diff-rename.sh

@@ -126,6 +126,21 @@ test_expect_success 'test diff.renames unset' '
 	compare_diff_patch current expected
 '
 
+test_expect_success 'diff.renameThreshold=100% suppresses inexact rename in diff' '
+	git -c diff.renameThreshold=100% diff --cached $tree >current &&
+	compare_diff_patch current no-rename
+'
+
+test_expect_success 'diff.renameThreshold=1% detects rename in diff' '
+	git -c diff.renameThreshold=1% diff --cached $tree >current &&
+	compare_diff_patch current expected
+'
+
+test_expect_success '-M overrides diff.renameThreshold' '
+	git -c diff.renameThreshold=100% diff -M --cached $tree >current &&
+	compare_diff_patch current expected
+'
+
 test_expect_success 'favour same basenames over different ones' '
 	cp path1 another-path &&
 	git add another-path &&
@@ -155,6 +170,16 @@ test_expect_success 'favour same basenames even with minor differences' '
 	test_grep "renamed: .*path1 -> subdir/path1" out
 '
 
+test_expect_success 'diff.renameThreshold with modified rename in status' '
+	git show HEAD:path1 | sed -e "s/Line 1/Changed 1/" \
+		-e "s/Line 2/Changed 2/" -e "s/Line 3/Changed 3/" >subdir/path1 &&
+	git add subdir/path1 &&
+	git -c diff.renameThreshold=100% status >out &&
+	test_grep ! "renamed:" out &&
+	git -c diff.renameThreshold=1% status >out &&
+	test_grep "renamed:" out
+'
+
 test_expect_success 'two files with same basename and same content' '
 	git reset --hard &&
 	mkdir -p dir/A dir/B &&

t/t6434-merge-recursive-rename-options.sh

@@ -332,4 +332,36 @@ test_expect_success 'merge.renames overrides diff.renames' '
 	$check_50
 '
 
+test_expect_success 'diff.renameThreshold sets merge threshold' '
+	git read-tree --reset -u HEAD &&
+	test_must_fail git -c diff.renameThreshold=$th0 merge-recursive $tail &&
+	check_threshold_0
+'
+
+test_expect_success 'diff.renameThreshold=100% limits to exact renames in merge' '
+	git read-tree --reset -u HEAD &&
+	test_must_fail git -c diff.renameThreshold=100% merge-recursive $tail &&
+	check_exact_renames
+'
+
+test_expect_success 'merge.renameThreshold overrides diff.renameThreshold' '
+	git read-tree --reset -u HEAD &&
+	test_must_fail git -c diff.renameThreshold=100% \
+		-c merge.renameThreshold=$th0 merge-recursive $tail &&
+	check_threshold_0
+'
+
+test_expect_success 'merge.renameThreshold defaults to diff.renameThreshold' '
+	git read-tree --reset -u HEAD &&
+	test_must_fail git -c diff.renameThreshold=$th2 merge-recursive $tail &&
+	check_threshold_2
+'
+
+test_expect_success '--find-renames overrides merge.renameThreshold' '
+	git read-tree --reset -u HEAD &&
+	test_must_fail git -c merge.renameThreshold=100% \
+		merge-recursive --find-renames=$th0 $tail &&
+	check_threshold_0
+'
+
 test_done

t/t7525-status-rename.sh

@@ -97,6 +97,38 @@ test_expect_success 'status score=01%' '
 	test_grep "renamed:" actual
 '
 
+test_expect_success 'diff.renameThreshold sets default threshold' '
+	git -c diff.renameThreshold=100% status >actual &&
+	test_grep "deleted:" actual &&
+	test_grep "new file:" actual
+'
+
+test_expect_success 'status.renameThreshold overrides diff.renameThreshold' '
+	git -c diff.renameThreshold=100% -c status.renameThreshold=01% status >actual &&
+	test_grep "renamed:" actual
+'
+
+test_expect_success 'diff.renameThreshold=01% detects rename in status' '
+	git -c diff.renameThreshold=01% status >actual &&
+	test_grep "renamed:" actual
+'
+
+test_expect_success 'commit honors diff.renameThreshold' '
+	git -c diff.renameThreshold=100% commit --dry-run >actual &&
+	test_grep "deleted:" actual &&
+	test_grep "new file:" actual
+'
+
+test_expect_success 'commit honors status.renameThreshold' '
+	git -c status.renameThreshold=01% commit --dry-run >actual &&
+	test_grep "renamed:" actual
+'
+
+test_expect_success '-M overrides status.renameThreshold' '
+	git -c status.renameThreshold=100% status -M=01% >actual &&
+	test_grep "renamed:" actual
+'
+
 test_expect_success 'copies not overridden by find-renames' '
 	cp renamed copy &&
 	git add copy &&