diff: implement config.diff.renames=copies-harder

Documentation/config/diff.txt

@@ -131,7 +131,8 @@ diff.renames::
 	Whether and how Git detects renames.  If set to "false",
 	rename detection is disabled. If set to "true", basic rename
 	detection is enabled.  If set to "copies" or "copy", Git will
-	detect copies, as well.  Defaults to true.  Note that this
+	detect copies, as well.  If set to "copies-harder", Git will try harder
+	to detect copies.  Defaults to true.  Note that this
 	affects only 'git diff' Porcelain like linkgit:git-diff[1] and
 	linkgit:git-log[1], and not lower level commands such as
 	linkgit:git-diff-files[1].

Documentation/config/status.txt

@@ -33,7 +33,8 @@ 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
 	disabled. If set to "true", basic rename detection is enabled.
-	If set to "copies" or "copy", Git will detect copies, as well.
+	If set to "copies" or "copy", Git will detect copies, as well.  If
+	set to "copies-harder", Git will try harder to detect copies.
 	Defaults to the value of diff.renames.
 
 status.showStash::

diff.c

@@ -206,8 +206,11 @@ int git_config_rename(const char *var, const char *value)
 {
 	if (!value)
 		return DIFF_DETECT_RENAME;
+	if (!strcasecmp(value, "copies-harder"))
+		return DIFF_DETECT_COPY_HARDER;
 	if (!strcasecmp(value, "copies") || !strcasecmp(value, "copy"))
-		return  DIFF_DETECT_COPY;
+		return DIFF_DETECT_COPY;
+
 	return git_config_bool(var,value) ? DIFF_DETECT_RENAME : 0;
 }
 
@@ -4832,8 +4835,11 @@ void diff_setup_done(struct diff_options *options)
 	else
 		options->flags.diff_from_contents = 0;
 
-	if (options->flags.find_copies_harder)
+	/* Just fold this in as it makes the patch-to-git smaller */
+	if (options->flags.find_copies_harder || options->detect_rename == DIFF_DETECT_COPY_HARDER) {
+		options->flags.find_copies_harder = 1;
 		options->detect_rename = DIFF_DETECT_COPY;
+	}
 
 	if (!options->flags.relative_name)
 		options->prefix = NULL;
@@ -5264,7 +5270,7 @@ static int diff_opt_find_copies(const struct option *opt,
 	if (*arg != 0)
 		return error(_("invalid argument to %s"), opt->long_name);
 
-	if (options->detect_rename == DIFF_DETECT_COPY)
+	if (options->detect_rename == DIFF_DETECT_COPY || options->detect_rename == DIFF_DETECT_COPY_HARDER)
 		options->flags.find_copies_harder = 1;
 	else
 		options->detect_rename = DIFF_DETECT_COPY;

diff.h

@@ -555,6 +555,7 @@ int git_config_rename(const char *var, const char *value);
 
 #define DIFF_DETECT_RENAME	1
 #define DIFF_DETECT_COPY	2
+#define DIFF_DETECT_COPY_HARDER 3
 
 #define DIFF_PICKAXE_ALL	1
 #define DIFF_PICKAXE_REGEX	2

diffcore-rename.c

@@ -299,7 +299,7 @@ static int find_identical_files(struct hashmap *srcs,
 		}
 		/* Give higher scores to sources that haven't been used already */
 		score = !source->rename_used;
-		if (source->rename_used && options->detect_rename != DIFF_DETECT_COPY)
+		if (source->rename_used && options->detect_rename != DIFF_DETECT_COPY && options->detect_rename != DIFF_DETECT_COPY_HARDER)
 			continue;
 		score += basename_same(source, target);
 		if (score > best_score) {
@@ -1405,7 +1405,7 @@ void diffcore_rename_extended(struct diff_options *options,
 	trace2_region_enter("diff", "setup", options->repo);
 	info.setup = 0;
 	assert(!dir_rename_count || strmap_empty(dir_rename_count));
-	want_copies = (detect_rename == DIFF_DETECT_COPY);
+	want_copies = (detect_rename == DIFF_DETECT_COPY || detect_rename == DIFF_DETECT_COPY_HARDER);
 	if (dirs_removed && (break_idx || want_copies))
 		BUG("dirs_removed incompatible with break/copy detection");
 	if (break_idx && relevant_sources)

merge-ort.c

@@ -4782,7 +4782,7 @@ static void merge_start(struct merge_options *opt, struct merge_result *result)
 	 * sanity check them anyway.
 	 */
 	assert(opt->detect_renames >= -1 &&
-	       opt->detect_renames <= DIFF_DETECT_COPY);
+	       opt->detect_renames <= DIFF_DETECT_COPY_HARDER);
 	assert(opt->verbosity >= 0 && opt->verbosity <= 5);
 	assert(opt->buffer_output <= 2);
 	assert(opt->obuf.len == 0);

merge-recursive.c

@@ -3708,7 +3708,7 @@ static int merge_start(struct merge_options *opt, struct tree *head)
 	assert(opt->branch1 && opt->branch2);
 
 	assert(opt->detect_renames >= -1 &&
-	       opt->detect_renames <= DIFF_DETECT_COPY);
+	       opt->detect_renames <= DIFF_DETECT_COPY_HARDER);
 	assert(opt->detect_directory_renames >= MERGE_DIRECTORY_RENAMES_NONE &&
 	       opt->detect_directory_renames <= MERGE_DIRECTORY_RENAMES_TRUE);
 	assert(opt->rename_limit >= -1);