1 files changed, 204 insertions, 161 deletions

diff --git a/diff.c b/diff.c
index 32142dba64..db952a5bc7 100644
--- a/diff.c
+++ b/diff.c
@@ -15,6 +15,7 @@
 #include "sigchain.h"
 #include "submodule.h"
 #include "ll-merge.h"
+#include "string-list.h"
 
 #ifdef NO_FAST_WORKING_DIRECTORY
 #define FAST_WORKING_DIRECTORY 0
@@ -25,7 +26,8 @@
 static int diff_detect_rename_default;
 static int diff_rename_limit_default = 400;
 static int diff_suppress_blank_empty;
-int diff_use_color_default = -1;
+static int diff_use_color_default = -1;
+static int diff_context_default = 3;
 static const char *diff_word_regex_cfg;
 static const char *external_diff_cmd_cfg;
 int diff_auto_refresh_index = 1;
@@ -34,6 +36,7 @@ static int diff_no_prefix;
 static int diff_stat_graph_width;
 static int diff_dirstat_permille_default = 30;
 static struct diff_options default_diff_options;
+static long diff_algorithm;
 
 static char diff_colors[][COLOR_MAXLEN] = {
 	GIT_COLOR_RESET,
@@ -68,26 +71,30 @@ static int parse_diff_color_slot(const char *var, int ofs)
 	return -1;
 }
 
-static int parse_dirstat_params(struct diff_options *options, const char *params,
+static int parse_dirstat_params(struct diff_options *options, const char *params_string,
 				struct strbuf *errmsg)
 {
-	const char *p = params;
-	int p_len, ret = 0;
+	char *params_copy = xstrdup(params_string);
+	struct string_list params = STRING_LIST_INIT_NODUP;
+	int ret = 0;
+	int i;
 
-	while (*p) {
-		p_len = strchrnul(p, ',') - p;
-		if (!memcmp(p, "changes", p_len)) {
+	if (*params_copy)
+		string_list_split_in_place(&params, params_copy, ',', -1);
+	for (i = 0; i < params.nr; i++) {
+		const char *p = params.items[i].string;
+		if (!strcmp(p, "changes")) {
 			DIFF_OPT_CLR(options, DIRSTAT_BY_LINE);
 			DIFF_OPT_CLR(options, DIRSTAT_BY_FILE);
-		} else if (!memcmp(p, "lines", p_len)) {
+		} else if (!strcmp(p, "lines")) {
 			DIFF_OPT_SET(options, DIRSTAT_BY_LINE);
 			DIFF_OPT_CLR(options, DIRSTAT_BY_FILE);
-		} else if (!memcmp(p, "files", p_len)) {
+		} else if (!strcmp(p, "files")) {
 			DIFF_OPT_CLR(options, DIRSTAT_BY_LINE);
 			DIFF_OPT_SET(options, DIRSTAT_BY_FILE);
-		} else if (!memcmp(p, "noncumulative", p_len)) {
+		} else if (!strcmp(p, "noncumulative")) {
 			DIFF_OPT_CLR(options, DIRSTAT_CUMULATIVE);
-		} else if (!memcmp(p, "cumulative", p_len)) {
+		} else if (!strcmp(p, "cumulative")) {
 			DIFF_OPT_SET(options, DIRSTAT_CUMULATIVE);
 		} else if (isdigit(*p)) {
 			char *end;
@@ -99,27 +106,35 @@ static int parse_dirstat_params(struct diff_options *options, const char *params
 				while (isdigit(*++end))
 					; /* nothing */
 			}
-			if (end - p == p_len)
+			if (!*end)
 				options->dirstat_permille = permille;
 			else {
-				strbuf_addf(errmsg, _("  Failed to parse dirstat cut-off percentage '%.*s'\n"),
-					    p_len, p);
+				strbuf_addf(errmsg, _("  Failed to parse dirstat cut-off percentage '%s'\n"),
+					    p);
 				ret++;
 			}
 		} else {
-			strbuf_addf(errmsg, _("  Unknown dirstat parameter '%.*s'\n"),
-				    p_len, p);
+			strbuf_addf(errmsg, _("  Unknown dirstat parameter '%s'\n"), p);
 			ret++;
 		}
 
-		p += p_len;
-
-		if (*p)
-			p++; /* more parameters, swallow separator */
 	}
+	string_list_clear(&params, 0);
+	free(params_copy);
 	return ret;
 }
 
+static int parse_submodule_params(struct diff_options *options, const char *value)
+{
+	if (!strcmp(value, "log"))
+		DIFF_OPT_SET(options, SUBMODULE_LOG);
+	else if (!strcmp(value, "short"))
+		DIFF_OPT_CLR(options, SUBMODULE_LOG);
+	else
+		return -1;
+	return 0;
+}
+
 static int git_config_rename(const char *var, const char *value)
 {
 	if (!value)
@@ -129,6 +144,21 @@ static int git_config_rename(const char *var, const char *value)
 	return git_config_bool(var,value) ? DIFF_DETECT_RENAME : 0;
 }
 
+long parse_algorithm_value(const char *value)
+{
+	if (!value)
+		return -1;
+	else if (!strcasecmp(value, "myers") || !strcasecmp(value, "default"))
+		return 0;
+	else if (!strcasecmp(value, "minimal"))
+		return XDF_NEED_MINIMAL;
+	else if (!strcasecmp(value, "patience"))
+		return XDF_PATIENCE_DIFF;
+	else if (!strcasecmp(value, "histogram"))
+		return XDF_HISTOGRAM_DIFF;
+	return -1;
+}
+
 /*
  * These are to give UI layer defaults.
  * The core-level commands such as git-diff-files should
@@ -141,6 +171,12 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 		diff_use_color_default = git_config_colorbool(var, value);
 		return 0;
 	}
+	if (!strcmp(var, "diff.context")) {
+		diff_context_default = git_config_int(var, value);
+		if (diff_context_default < 0)
+			return -1;
+		return 0;
+	}
 	if (!strcmp(var, "diff.renames")) {
 		diff_detect_rename_default = git_config_rename(var, value);
 		return 0;
@@ -169,6 +205,20 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
 	if (!strcmp(var, "diff.ignoresubmodules"))
 		handle_ignore_submodules_arg(&default_diff_options, value);
 
+	if (!strcmp(var, "diff.submodule")) {
+		if (parse_submodule_params(&default_diff_options, value))
+			warning(_("Unknown value for 'diff.submodule' config variable: '%s'"),
+				value);
+		return 0;
+	}
+
+	if (!strcmp(var, "diff.algorithm")) {
+		diff_algorithm = parse_algorithm_value(value);
+		if (diff_algorithm < 0)
+			return -1;
+		return 0;
+	}
+
 	if (git_color_config(var, value, cb) < 0)
 		return -1;
 
@@ -375,12 +425,7 @@ static void emit_line_0(struct diff_options *o, const char *set, const char *res
 	int nofirst;
 	FILE *file = o->file;
 
-	if (o->output_prefix) {
-		struct strbuf *msg = NULL;
-		msg = o->output_prefix(o, o->output_prefix_data);
-		assert(msg);
-		fwrite(msg->buf, msg->len, 1, file);
-	}
+	fputs(diff_line_prefix(o), file);
 
 	if (len == 0) {
 		has_trailing_newline = (first == '\n');
@@ -598,13 +643,7 @@ static void emit_rewrite_diff(const char *name_a,
 	char *data_one, *data_two;
 	size_t size_one, size_two;
 	struct emit_callback ecbdata;
-	char *line_prefix = "";
-	struct strbuf *msgbuf;
-
-	if (o && o->output_prefix) {
-		msgbuf = o->output_prefix(o, o->output_prefix_data);
-		line_prefix = msgbuf->buf;
-	}
+	const char *line_prefix = diff_line_prefix(o);
 
 	if (diff_mnemonic_prefix && DIFF_OPT_TST(o, REVERSE_DIFF)) {
 		a_prefix = o->b_prefix;
@@ -800,18 +839,14 @@ static void fn_out_diff_words_aux(void *priv, char *line, unsigned long len)
 	int minus_first, minus_len, plus_first, plus_len;
 	const char *minus_begin, *minus_end, *plus_begin, *plus_end;
 	struct diff_options *opt = diff_words->opt;
-	struct strbuf *msgbuf;
-	char *line_prefix = "";
+	const char *line_prefix;
 
 	if (line[0] != '@' || parse_hunk_header(line, len,
 			&minus_first, &minus_len, &plus_first, &plus_len))
 		return;
 
 	assert(opt);
-	if (opt->output_prefix) {
-		msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
-		line_prefix = msgbuf->buf;
-	}
+	line_prefix = diff_line_prefix(opt);
 
 	/* POSIX requires that first be decremented by one if len == 0... */
 	if (minus_len) {
@@ -935,14 +970,10 @@ static void diff_words_show(struct diff_words_data *diff_words)
 	struct diff_words_style *style = diff_words->style;
 
 	struct diff_options *opt = diff_words->opt;
-	struct strbuf *msgbuf;
-	char *line_prefix = "";
+	const char *line_prefix;
 
 	assert(opt);
-	if (opt->output_prefix) {
-		msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
-		line_prefix = msgbuf->buf;
-	}
+	line_prefix = diff_line_prefix(opt);
 
 	/* special case: only removal */
 	if (!diff_words->plus.text.size) {
@@ -1078,6 +1109,16 @@ const char *diff_get_color(int diff_use_color, enum color_diff ix)
 	return "";
 }
 
+const char *diff_line_prefix(struct diff_options *opt)
+{
+	struct strbuf *msgbuf;
+	if (!opt->output_prefix)
+		return "";
+
+	msgbuf = opt->output_prefix(opt, opt->output_prefix_data);
+	return msgbuf->buf;
+}
+
 static unsigned long sane_truncate_line(struct emit_callback *ecb, char *line, unsigned long len)
 {
 	const char *cp;
@@ -1118,13 +1159,7 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
 	const char *plain = diff_get_color(ecbdata->color_diff, DIFF_PLAIN);
 	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
 	struct diff_options *o = ecbdata->opt;
-	char *line_prefix = "";
-	struct strbuf *msgbuf;
-
-	if (o && o->output_prefix) {
-		msgbuf = o->output_prefix(o, o->output_prefix_data);
-		line_prefix = msgbuf->buf;
-	}
+	const char *line_prefix = diff_line_prefix(o);
 
 	if (ecbdata->header) {
 		fprintf(ecbdata->opt->file, "%s", ecbdata->header->buf);
@@ -1229,6 +1264,7 @@ static char *pprint_rename(const char *a, const char *b)
 	const char *new = b;
 	struct strbuf name = STRBUF_INIT;
 	int pfx_length, sfx_length;
+	int pfx_adjust_for_slash;
 	int len_a = strlen(a);
 	int len_b = strlen(b);
 	int a_midlen, b_midlen;
@@ -1255,7 +1291,18 @@ static char *pprint_rename(const char *a, const char *b)
 	old = a + len_a;
 	new = b + len_b;
 	sfx_length = 0;
-	while (a <= old && b <= new && *old == *new) {
+	/*
+	 * If there is a common prefix, it must end in a slash.  In
+	 * that case we let this loop run 1 into the prefix to see the
+	 * same slash.
+	 *
+	 * If there is no common prefix, we cannot do this as it would
+	 * underrun the input strings.
+	 */
+	pfx_adjust_for_slash = (pfx_length ? 1 : 0);
+	while (a + pfx_length - pfx_adjust_for_slash <= old &&
+	       b + pfx_length - pfx_adjust_for_slash <= new &&
+	       *old == *new) {
 		if (*old == '/')
 			sfx_length = len_a - (old - a);
 		old--;
@@ -1300,6 +1347,7 @@ struct diffstat_t {
 		unsigned is_unmerged:1;
 		unsigned is_binary:1;
 		unsigned is_renamed:1;
+		unsigned is_interesting:1;
 		uintmax_t added, deleted;
 	} **files;
 };
@@ -1447,16 +1495,11 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	const char *reset, *add_c, *del_c;
 	const char *line_prefix = "";
 	int extra_shown = 0;
-	struct strbuf *msg = NULL;
 
 	if (data->nr == 0)
 		return;
 
-	if (options->output_prefix) {
-		msg = options->output_prefix(options, options->output_prefix_data);
-		line_prefix = msg->buf;
-	}
-
+	line_prefix = diff_line_prefix(options);
 	count = options->stat_count ? options->stat_count : data->nr;
 
 	reset = diff_get_color_opt(options, DIFF_RESET);
@@ -1469,8 +1512,8 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	for (i = 0; (i < count) && (i < data->nr); i++) {
 		struct diffstat_file *file = data->files[i];
 		uintmax_t change = file->added + file->deleted;
-		if (!data->files[i]->is_renamed &&
-			 (change == 0)) {
+
+		if (!file->is_interesting && (change == 0)) {
 			count++; /* not shown == room for one more */
 			continue;
 		}
@@ -1497,7 +1540,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		if (max_change < change)
 			max_change = change;
 	}
-	count = i; /* min(count, data->nr) */
+	count = i; /* where we can stop scanning in data->files[] */
 
 	/*
 	 * We have width = stat_width or term_columns() columns total.
@@ -1585,16 +1628,15 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 	 */
 	for (i = 0; i < count; i++) {
 		const char *prefix = "";
-		char *name = data->files[i]->print_name;
-		uintmax_t added = data->files[i]->added;
-		uintmax_t deleted = data->files[i]->deleted;
+		struct diffstat_file *file = data->files[i];
+		char *name = file->print_name;
+		uintmax_t added = file->added;
+		uintmax_t deleted = file->deleted;
 		int name_len;
 
-		if (!data->files[i]->is_renamed &&
-			 (added + deleted == 0)) {
-			total_files--;
+		if (!file->is_interesting && (added + deleted == 0))
 			continue;
-		}
+
 		/*
 		 * "scale" the filename
 		 */
@@ -1610,7 +1652,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 				name = slash;
 		}
 
-		if (data->files[i]->is_binary) {
+		if (file->is_binary) {
 			fprintf(options->file, "%s", line_prefix);
 			show_name(options->file, prefix, name, len);
 			fprintf(options->file, " %*s", number_width, "Bin");
@@ -1627,7 +1669,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 			fprintf(options->file, "\n");
 			continue;
 		}
-		else if (data->files[i]->is_unmerged) {
+		else if (file->is_unmerged) {
 			fprintf(options->file, "%s", line_prefix);
 			show_name(options->file, prefix, name, len);
 			fprintf(options->file, " Unmerged\n");
@@ -1639,8 +1681,6 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		 */
 		add = added;
 		del = deleted;
-		adds += add;
-		dels += del;
 
 		if (graph_width <= max_change) {
 			int total = add + del;
@@ -1666,16 +1706,24 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
 		show_graph(options->file, '-', del, del_c, reset);
 		fprintf(options->file, "\n");
 	}
-	for (i = count; i < data->nr; i++) {
-		uintmax_t added = data->files[i]->added;
-		uintmax_t deleted = data->files[i]->deleted;
-		if (!data->files[i]->is_renamed &&
-			 (added + deleted == 0)) {
+
+	for (i = 0; i < data->nr; i++) {
+		struct diffstat_file *file = data->files[i];
+		uintmax_t added = file->added;
+		uintmax_t deleted = file->deleted;
+
+		if (file->is_unmerged ||
+		    (!file->is_interesting && (added + deleted == 0))) {
 			total_files--;
 			continue;
 		}
-		adds += added;
-		dels += deleted;
+
+		if (!file->is_binary) {
+			adds += added;
+			dels += deleted;
+		}
+		if (i < count)
+			continue;
 		if (!extra_shown)
 			fprintf(options->file, "%s ...\n", line_prefix);
 		extra_shown = 1;
@@ -1695,21 +1743,15 @@ static void show_shortstats(struct diffstat_t *data, struct diff_options *option
 		int added = data->files[i]->added;
 		int deleted= data->files[i]->deleted;
 
-		if (data->files[i]->is_unmerged)
-			continue;
-		if (!data->files[i]->is_renamed && (added + deleted == 0)) {
+		if (data->files[i]->is_unmerged ||
+		    (!data->files[i]->is_interesting && (added + deleted == 0))) {
 			total_files--;
 		} else if (!data->files[i]->is_binary) { /* don't count bytes */
 			adds += added;
 			dels += deleted;
 		}
 	}
-	if (options->output_prefix) {
-		struct strbuf *msg = NULL;
-		msg = options->output_prefix(options,
-				options->output_prefix_data);
-		fprintf(options->file, "%s", msg->buf);
-	}
+	fprintf(options->file, "%s", diff_line_prefix(options));
 	print_stat_summary(options->file, total_files, adds, dels);
 }
 
@@ -1723,12 +1765,7 @@ static void show_numstat(struct diffstat_t *data, struct diff_options *options)
 	for (i = 0; i < data->nr; i++) {
 		struct diffstat_file *file = data->files[i];
 
-		if (options->output_prefix) {
-			struct strbuf *msg = NULL;
-			msg = options->output_prefix(options,
-					options->output_prefix_data);
-			fprintf(options->file, "%s", msg->buf);
-		}
+		fprintf(options->file, "%s", diff_line_prefix(options));
 
 		if (file->is_binary)
 			fprintf(options->file, "-\t-\t");
@@ -1770,13 +1807,7 @@ static long gather_dirstat(struct diff_options *opt, struct dirstat_dir *dir,
 {
 	unsigned long this_dir = 0;
 	unsigned int sources = 0;
-	const char *line_prefix = "";
-	struct strbuf *msg = NULL;
-
-	if (opt->output_prefix) {
-		msg = opt->output_prefix(opt, opt->output_prefix_data);
-		line_prefix = msg->buf;
-	}
+	const char *line_prefix = diff_line_prefix(opt);
 
 	while (dir->nr) {
 		struct dirstat_file *f = dir->files;
@@ -2026,15 +2057,10 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
 	const char *reset = diff_get_color(data->o->use_color, DIFF_RESET);
 	const char *set = diff_get_color(data->o->use_color, DIFF_FILE_NEW);
 	char *err;
-	char *line_prefix = "";
-	struct strbuf *msgbuf;
+	const char *line_prefix;
 
 	assert(data->o);
-	if (data->o->output_prefix) {
-		msgbuf = data->o->output_prefix(data->o,
-			data->o->output_prefix_data);
-		line_prefix = msgbuf->buf;
-	}
+	line_prefix = diff_line_prefix(data->o);
 
 	if (line[0] == '+') {
 		unsigned bad;
@@ -2091,7 +2117,8 @@ static unsigned char *deflate_it(char *data,
 	return deflated;
 }
 
-static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two, char *prefix)
+static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two,
+				  const char *prefix)
 {
 	void *cp;
 	void *delta;
@@ -2152,7 +2179,8 @@ static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two, char
 	free(data);
 }
 
-static void emit_binary_diff(FILE *file, mmfile_t *one, mmfile_t *two, char *prefix)
+static void emit_binary_diff(FILE *file, mmfile_t *one, mmfile_t *two,
+			     const char *prefix)
 {
 	fprintf(file, "%sGIT binary patch\n", prefix);
 	emit_binary_diff_body(file, one, two, prefix);
@@ -2213,19 +2241,13 @@ static void builtin_diff(const char *name_a,
 	mmfile_t mf1, mf2;
 	const char *lbl[2];
 	char *a_one, *b_two;
-	const char *set = diff_get_color_opt(o, DIFF_METAINFO);
+	const char *meta = diff_get_color_opt(o, DIFF_METAINFO);
 	const char *reset = diff_get_color_opt(o, DIFF_RESET);
 	const char *a_prefix, *b_prefix;
 	struct userdiff_driver *textconv_one = NULL;
 	struct userdiff_driver *textconv_two = NULL;
 	struct strbuf header = STRBUF_INIT;
-	struct strbuf *msgbuf;
-	char *line_prefix = "";
-
-	if (o->output_prefix) {
-		msgbuf = o->output_prefix(o, o->output_prefix_data);
-		line_prefix = msgbuf->buf;
-	}
+	const char *line_prefix = diff_line_prefix(o);
 
 	if (DIFF_OPT_TST(o, SUBMODULE_LOG) &&
 			(!one->mode || S_ISGITLINK(one->mode)) &&
@@ -2234,7 +2256,7 @@ static void builtin_diff(const char *name_a,
 		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
 		show_submodule_summary(o->file, one ? one->path : two->path,
 				one->sha1, two->sha1, two->dirty_submodule,
-				del, add, reset);
+				meta, del, add, reset);
 		return;
 	}
 
@@ -2260,24 +2282,24 @@ static void builtin_diff(const char *name_a,
 	b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
 	lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
 	lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
-	strbuf_addf(&header, "%s%sdiff --git %s %s%s\n", line_prefix, set, a_one, b_two, reset);
+	strbuf_addf(&header, "%s%sdiff --git %s %s%s\n", line_prefix, meta, a_one, b_two, reset);
 	if (lbl[0][0] == '/') {
 		/* /dev/null */
-		strbuf_addf(&header, "%s%snew file mode %06o%s\n", line_prefix, set, two->mode, reset);
+		strbuf_addf(&header, "%s%snew file mode %06o%s\n", line_prefix, meta, two->mode, reset);
 		if (xfrm_msg)
 			strbuf_addstr(&header, xfrm_msg);
 		must_show_header = 1;
 	}
 	else if (lbl[1][0] == '/') {
-		strbuf_addf(&header, "%s%sdeleted file mode %06o%s\n", line_prefix, set, one->mode, reset);
+		strbuf_addf(&header, "%s%sdeleted file mode %06o%s\n", line_prefix, meta, one->mode, reset);
 		if (xfrm_msg)
 			strbuf_addstr(&header, xfrm_msg);
 		must_show_header = 1;
 	}
 	else {
 		if (one->mode != two->mode) {
-			strbuf_addf(&header, "%s%sold mode %06o%s\n", line_prefix, set, one->mode, reset);
-			strbuf_addf(&header, "%s%snew mode %06o%s\n", line_prefix, set, two->mode, reset);
+			strbuf_addf(&header, "%s%sold mode %06o%s\n", line_prefix, meta, one->mode, reset);
+			strbuf_addf(&header, "%s%snew mode %06o%s\n", line_prefix, meta, two->mode, reset);
 			must_show_header = 1;
 		}
 		if (xfrm_msg)
@@ -2397,13 +2419,20 @@ static void builtin_diffstat(const char *name_a, const char *name_b,
 			     struct diff_filespec *two,
 			     struct diffstat_t *diffstat,
 			     struct diff_options *o,
-			     int complete_rewrite)
+			     struct diff_filepair *p)
 {
 	mmfile_t mf1, mf2;
 	struct diffstat_file *data;
 	int same_contents;
+	int complete_rewrite = 0;
+
+	if (!DIFF_PAIR_UNMERGED(p)) {
+		if (p->status == DIFF_STATUS_MODIFIED && p->score)
+			complete_rewrite = 1;
+	}
 
 	data = diffstat_add(diffstat, name_a, name_b);
+	data->is_interesting = p->status != DIFF_STATUS_UNKNOWN;
 
 	if (!one || !two) {
 		data->is_unmerged = 1;
@@ -2917,14 +2946,9 @@ static void fill_metainfo(struct strbuf *msg,
 {
 	const char *set = diff_get_color(use_color, DIFF_METAINFO);
 	const char *reset = diff_get_color(use_color, DIFF_RESET);
-	struct strbuf *msgbuf;
-	char *line_prefix = "";
+	const char *line_prefix = diff_line_prefix(o);
 
 	*must_show_header = 1;
-	if (o->output_prefix) {
-		msgbuf = o->output_prefix(o, o->output_prefix_data);
-		line_prefix = msgbuf->buf;
-	}
 	strbuf_init(msg, PATH_MAX * 2 + 300);
 	switch (p->status) {
 	case DIFF_STATUS_COPIED:
@@ -3114,11 +3138,10 @@ static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
 {
 	const char *name;
 	const char *other;
-	int complete_rewrite = 0;
 
 	if (DIFF_PAIR_UNMERGED(p)) {
 		/* unmerged */
-		builtin_diffstat(p->one->path, NULL, NULL, NULL, diffstat, o, 0);
+		builtin_diffstat(p->one->path, NULL, NULL, NULL, diffstat, o, p);
 		return;
 	}
 
@@ -3131,9 +3154,7 @@ static void run_diffstat(struct diff_filepair *p, struct diff_options *o,
 	diff_fill_sha1_info(p->one);
 	diff_fill_sha1_info(p->two);
 
-	if (p->status == DIFF_STATUS_MODIFIED && p->score)
-		complete_rewrite = 1;
-	builtin_diffstat(name, other, p->one, p->two, diffstat, o, complete_rewrite);
+	builtin_diffstat(name, other, p->one, p->two, diffstat, o, p);
 }
 
 static void run_checkdiff(struct diff_filepair *p, struct diff_options *o)
@@ -3170,13 +3191,14 @@ void diff_setup(struct diff_options *options)
 	options->break_opt = -1;
 	options->rename_limit = -1;
 	options->dirstat_permille = diff_dirstat_permille_default;
-	options->context = 3;
+	options->context = diff_context_default;
 	DIFF_OPT_SET(options, RENAME_EMPTY);
 
 	options->change = diff_change;
 	options->add_remove = diff_addremove;
 	options->use_color = diff_use_color_default;
 	options->detect_rename = diff_detect_rename_default;
+	options->xdl_opts |= diff_algorithm;
 
 	if (diff_no_prefix) {
 		options->a_prefix = options->b_prefix = "";
@@ -3466,6 +3488,14 @@ static int parse_dirstat_opt(struct diff_options *options, const char *params)
 	return 1;
 }
 
+static int parse_submodule_opt(struct diff_options *options, const char *value)
+{
+	if (parse_submodule_params(options, value))
+		die(_("Failed to parse --submodule option parameter: '%s'"),
+			value);
+	return 1;
+}
+
 int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 {
 	const char *arg = av[0];
@@ -3566,6 +3596,16 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		options->xdl_opts = DIFF_WITH_ALG(options, PATIENCE_DIFF);
 	else if (!strcmp(arg, "--histogram"))
 		options->xdl_opts = DIFF_WITH_ALG(options, HISTOGRAM_DIFF);
+	else if (!prefixcmp(arg, "--diff-algorithm=")) {
+		long value = parse_algorithm_value(arg+17);
+		if (value < 0)
+			return error("option diff-algorithm accepts \"myers\", "
+				     "\"minimal\", \"patience\" and \"histogram\"");
+		/* clear out previous settings */
+		DIFF_XDL_CLR(options, NEED_MINIMAL);
+		options->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
+		options->xdl_opts |= value;
+	}
 
 	/* flags options */
 	else if (!strcmp(arg, "--binary")) {
@@ -3582,6 +3622,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		DIFF_OPT_SET(options, FIND_COPIES_HARDER);
 	else if (!strcmp(arg, "--follow"))
 		DIFF_OPT_SET(options, FOLLOW_RENAMES);
+	else if (!strcmp(arg, "--no-follow"))
+		DIFF_OPT_CLR(options, FOLLOW_RENAMES);
 	else if (!strcmp(arg, "--color"))
 		options->use_color = 1;
 	else if (!prefixcmp(arg, "--color=")) {
@@ -3646,10 +3688,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		handle_ignore_submodules_arg(options, arg + 20);
 	} else if (!strcmp(arg, "--submodule"))
 		DIFF_OPT_SET(options, SUBMODULE_LOG);
-	else if (!prefixcmp(arg, "--submodule=")) {
-		if (!strcmp(arg + 12, "log"))
-			DIFF_OPT_SET(options, SUBMODULE_LOG);
-	}
+	else if (!prefixcmp(arg, "--submodule="))
+		return parse_submodule_opt(options, arg + 12);
 
 	/* misc options */
 	else if (!strcmp(arg, "-z"))
@@ -3856,12 +3896,8 @@ static void diff_flush_raw(struct diff_filepair *p, struct diff_options *opt)
 {
 	int line_termination = opt->line_termination;
 	int inter_name_termination = line_termination ? '\t' : '\0';
-	if (opt->output_prefix) {
-		struct strbuf *msg = NULL;
-		msg = opt->output_prefix(opt, opt->output_prefix_data);
-		fprintf(opt->file, "%s", msg->buf);
-	}
 
+	fprintf(opt->file, "%s", diff_line_prefix(opt));
 	if (!(opt->output_format & DIFF_FORMAT_NAME_STATUS)) {
 		fprintf(opt->file, ":%06o %06o %s ", p->one->mode, p->two->mode,
 			diff_unique_abbrev(p->one->sha1, opt->abbrev));
@@ -4131,12 +4167,7 @@ static void show_rename_copy(FILE *file, const char *renamecopy, struct diff_fil
 static void diff_summary(struct diff_options *opt, struct diff_filepair *p)
 {
 	FILE *file = opt->file;
-	char *line_prefix = "";
-
-	if (opt->output_prefix) {
-		struct strbuf *buf = opt->output_prefix(opt, opt->output_prefix_data);
-		line_prefix = buf->buf;
-	}
+	const char *line_prefix = diff_line_prefix(opt);
 
 	switch(p->status) {
 	case DIFF_STATUS_DELETED:
@@ -4437,13 +4468,9 @@ void diff_flush(struct diff_options *options)
 
 	if (output_format & DIFF_FORMAT_PATCH) {
 		if (separator) {
-			if (options->output_prefix) {
-				struct strbuf *msg = NULL;
-				msg = options->output_prefix(options,
-					options->output_prefix_data);
-				fwrite(msg->buf, msg->len, 1, stdout);
-			}
-			putc(options->line_termination, options->file);
+			fprintf(options->file, "%s%c",
+				diff_line_prefix(options),
+				options->line_termination);
 			if (options->stat_sep) {
 				/* attach patch instead of inline */
 				fputs(options->stat_sep, options->file);
@@ -4647,7 +4674,7 @@ int diff_result_code(struct diff_options *opt, int status)
 {
 	int result = 0;
 
-	diff_warn_rename_limit("diff.renamelimit",
+	diff_warn_rename_limit("diff.renameLimit",
 			       opt->needed_rename_limit,
 			       opt->degraded_cc_to_c);
 	if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
@@ -4871,3 +4898,19 @@ size_t fill_textconv(struct userdiff_driver *driver,
 
 	return size;
 }
+
+void setup_diff_pager(struct diff_options *opt)
+{
+	/*
+	 * If the user asked for our exit code, then either they want --quiet
+	 * or --exit-code. We should definitely not bother with a pager in the
+	 * former case, as we will generate no output. Since we still properly
+	 * report our exit code even when a pager is run, we _could_ run a
+	 * pager with --exit-code. But since we have not done so historically,
+	 * and because it is easy to find people oneline advising "git diff
+	 * --exit-code" in hooks and other scripts, we do not do so.
+	 */
+	if (!DIFF_OPT_TST(opt, EXIT_WITH_STATUS) &&
+	    check_pager_config("diff") != 0)
+		setup_pager();
+}