/*
 * Copyright (C) 2005 Junio C Hamano
 */
#include "cache.h"
#include "config.h"
#include "tempfile.h"
#include "quote.h"
#include "diff.h"
#include "diffcore.h"
#include "delta.h"
#include "xdiff-interface.h"
#include "color.h"
#include "attr.h"
#include "run-command.h"
#include "utf8.h"
#include "userdiff.h"
#include "submodule-config.h"
#include "submodule.h"
#include "ll-merge.h"
#include "string-list.h"
#include "argv-array.h"
#include "graph.h"

#ifdef NO_FAST_WORKING_DIRECTORY
#define FAST_WORKING_DIRECTORY 0
#else
#define FAST_WORKING_DIRECTORY 1
#endif

static int diff_detect_rename_default;
static int diff_indent_heuristic = 1;
static int diff_rename_limit_default = 400;
static int diff_suppress_blank_empty;
static int diff_use_color_default = -1;
static int diff_context_default = 3;
static int diff_interhunk_context_default;
static const char *diff_word_regex_cfg;
static const char *external_diff_cmd_cfg;
static const char *diff_order_file_cfg;
int diff_auto_refresh_index = 1;
static int diff_mnemonic_prefix;
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 unsigned ws_error_highlight_default = WSEH_NEW;

static char diff_colors[][COLOR_MAXLEN] = {
	GIT_COLOR_RESET,
	GIT_COLOR_NORMAL,	/* CONTEXT */
	GIT_COLOR_BOLD,		/* METAINFO */
	GIT_COLOR_CYAN,		/* FRAGINFO */
	GIT_COLOR_RED,		/* OLD */
	GIT_COLOR_GREEN,	/* NEW */
	GIT_COLOR_YELLOW,	/* COMMIT */
	GIT_COLOR_BG_RED,	/* WHITESPACE */
	GIT_COLOR_NORMAL,	/* FUNCINFO */
};

static NORETURN void die_want_option(const char *option_name)
{
	die(_("option '%s' requires a value"), option_name);
}

static int parse_diff_color_slot(const char *var)
{
	if (!strcasecmp(var, "context") || !strcasecmp(var, "plain"))
		return DIFF_CONTEXT;
	if (!strcasecmp(var, "meta"))
		return DIFF_METAINFO;
	if (!strcasecmp(var, "frag"))
		return DIFF_FRAGINFO;
	if (!strcasecmp(var, "old"))
		return DIFF_FILE_OLD;
	if (!strcasecmp(var, "new"))
		return DIFF_FILE_NEW;
	if (!strcasecmp(var, "commit"))
		return DIFF_COMMIT;
	if (!strcasecmp(var, "whitespace"))
		return DIFF_WHITESPACE;
	if (!strcasecmp(var, "func"))
		return DIFF_FUNCINFO;
	return -1;
}

static int parse_dirstat_params(struct diff_options *options, const char *params_string,
				struct strbuf *errmsg)
{
	char *params_copy = xstrdup(params_string);
	struct string_list params = STRING_LIST_INIT_NODUP;
	int ret = 0;
	int i;

	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 (!strcmp(p, "lines")) {
			DIFF_OPT_SET(options, DIRSTAT_BY_LINE);
			DIFF_OPT_CLR(options, DIRSTAT_BY_FILE);
		} else if (!strcmp(p, "files")) {
			DIFF_OPT_CLR(options, DIRSTAT_BY_LINE);
			DIFF_OPT_SET(options, DIRSTAT_BY_FILE);
		} else if (!strcmp(p, "noncumulative")) {
			DIFF_OPT_CLR(options, DIRSTAT_CUMULATIVE);
		} else if (!strcmp(p, "cumulative")) {
			DIFF_OPT_SET(options, DIRSTAT_CUMULATIVE);
		} else if (isdigit(*p)) {
			char *end;
			int permille = strtoul(p, &end, 10) * 10;
			if (*end == '.' && isdigit(*++end)) {
				/* only use first digit */
				permille += *end - '0';
				/* .. and ignore any further digits */
				while (isdigit(*++end))
					; /* nothing */
			}
			if (!*end)
				options->dirstat_permille = permille;
			else {
				strbuf_addf(errmsg, _("  Failed to parse dirstat cut-off percentage '%s'\n"),
					    p);
				ret++;
			}
		} else {
			strbuf_addf(errmsg, _("  Unknown dirstat parameter '%s'\n"), p);
			ret++;
		}

	}
	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"))
		options->submodule_format = DIFF_SUBMODULE_LOG;
	else if (!strcmp(value, "short"))
		options->submodule_format = DIFF_SUBMODULE_SHORT;
	else if (!strcmp(value, "diff"))
		options->submodule_format = DIFF_SUBMODULE_INLINE_DIFF;
	else
		return -1;
	return 0;
}

static int git_config_rename(const char *var, const char *value)
{
	if (!value)
		return DIFF_DETECT_RENAME;
	if (!strcasecmp(value, "copies") || !strcasecmp(value, "copy"))
		return  DIFF_DETECT_COPY;
	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;
}

static int parse_one_token(const char **arg, const char *token)
{
	const char *rest;
	if (skip_prefix(*arg, token, &rest) && (!*rest || *rest == ',')) {
		*arg = rest;
		return 1;
	}
	return 0;
}

static int parse_ws_error_highlight(const char *arg)
{
	const char *orig_arg = arg;
	unsigned val = 0;

	while (*arg) {
		if (parse_one_token(&arg, "none"))
			val = 0;
		else if (parse_one_token(&arg, "default"))
			val = WSEH_NEW;
		else if (parse_one_token(&arg, "all"))
			val = WSEH_NEW | WSEH_OLD | WSEH_CONTEXT;
		else if (parse_one_token(&arg, "new"))
			val |= WSEH_NEW;
		else if (parse_one_token(&arg, "old"))
			val |= WSEH_OLD;
		else if (parse_one_token(&arg, "context"))
			val |= WSEH_CONTEXT;
		else {
			return -1 - (int)(arg - orig_arg);
		}
		if (*arg)
			arg++;
	}
	return val;
}

/*
 * These are to give UI layer defaults.
 * The core-level commands such as git-diff-files should
 * never be affected by the setting of diff.renames
 * the user happens to have in the configuration file.
 */
void init_diff_ui_defaults(void)
{
	diff_detect_rename_default = 1;
}

int git_diff_heuristic_config(const char *var, const char *value, void *cb)
{
	if (!strcmp(var, "diff.indentheuristic"))
		diff_indent_heuristic = git_config_bool(var, value);
	return 0;
}

int git_diff_ui_config(const char *var, const char *value, void *cb)
{
	if (!strcmp(var, "diff.color") || !strcmp(var, "color.diff")) {
		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.interhunkcontext")) {
		diff_interhunk_context_default = git_config_int(var, value);
		if (diff_interhunk_context_default < 0)
			return -1;
		return 0;
	}
	if (!strcmp(var, "diff.renames")) {
		diff_detect_rename_default = git_config_rename(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.autorefreshindex")) {
		diff_auto_refresh_index = git_config_bool(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.mnemonicprefix")) {
		diff_mnemonic_prefix = git_config_bool(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.noprefix")) {
		diff_no_prefix = git_config_bool(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.statgraphwidth")) {
		diff_stat_graph_width = git_config_int(var, value);
		return 0;
	}
	if (!strcmp(var, "diff.external"))
		return git_config_string(&external_diff_cmd_cfg, var, value);
	if (!strcmp(var, "diff.wordregex"))
		return git_config_string(&diff_word_regex_cfg, var, value);
	if (!strcmp(var, "diff.orderfile"))
		return git_config_pathname(&diff_order_file_cfg, var, value);

	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 (!strcmp(var, "diff.wserrorhighlight")) {
		int val = parse_ws_error_highlight(value);
		if (val < 0)
			return -1;
		ws_error_highlight_default = val;
		return 0;
	}

	return git_diff_basic_config(var, value, cb);
}

int git_diff_basic_config(const char *var, const char *value, void *cb)
{
	const char *name;

	if (!strcmp(var, "diff.renamelimit")) {
		diff_rename_limit_default = git_config_int(var, value);
		return 0;
	}

	if (userdiff_config(var, value) < 0)
		return -1;

	if (skip_prefix(var, "diff.color.", &name) ||
	    skip_prefix(var, "color.diff.", &name)) {
		int slot = parse_diff_color_slot(name);
		if (slot < 0)
			return 0;
		if (!value)
			return config_error_nonbool(var);
		return color_parse(value, diff_colors[slot]);
	}

	/* like GNU diff's --suppress-blank-empty option  */
	if (!strcmp(var, "diff.suppressblankempty") ||
			/* for backwards compatibility */
			!strcmp(var, "diff.suppress-blank-empty")) {
		diff_suppress_blank_empty = git_config_bool(var, value);
		return 0;
	}

	if (!strcmp(var, "diff.dirstat")) {
		struct strbuf errmsg = STRBUF_INIT;
		default_diff_options.dirstat_permille = diff_dirstat_permille_default;
		if (parse_dirstat_params(&default_diff_options, value, &errmsg))
			warning(_("Found errors in 'diff.dirstat' config variable:\n%s"),
				errmsg.buf);
		strbuf_release(&errmsg);
		diff_dirstat_permille_default = default_diff_options.dirstat_permille;
		return 0;
	}

	if (starts_with(var, "submodule."))
		return parse_submodule_config_option(var, value);

	if (git_diff_heuristic_config(var, value, cb) < 0)
		return -1;

	return git_default_config(var, value, cb);
}

static char *quote_two(const char *one, const char *two)
{
	int need_one = quote_c_style(one, NULL, NULL, 1);
	int need_two = quote_c_style(two, NULL, NULL, 1);
	struct strbuf res = STRBUF_INIT;

	if (need_one + need_two) {
		strbuf_addch(&res, '"');
		quote_c_style(one, &res, NULL, 1);
		quote_c_style(two, &res, NULL, 1);
		strbuf_addch(&res, '"');
	} else {
		strbuf_addstr(&res, one);
		strbuf_addstr(&res, two);
	}
	return strbuf_detach(&res, NULL);
}

static const char *external_diff(void)
{
	static const char *external_diff_cmd = NULL;
	static int done_preparing = 0;

	if (done_preparing)
		return external_diff_cmd;
	external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
	if (!external_diff_cmd)
		external_diff_cmd = external_diff_cmd_cfg;
	done_preparing = 1;
	return external_diff_cmd;
}

/*
 * Keep track of files used for diffing. Sometimes such an entry
 * refers to a temporary file, sometimes to an existing file, and
 * sometimes to "/dev/null".
 */
static struct diff_tempfile {
	/*
	 * filename external diff should read from, or NULL if this
	 * entry is currently not in use:
	 */
	const char *name;

	char hex[GIT_MAX_HEXSZ + 1];
	char mode[10];

	/*
	 * If this diff_tempfile instance refers to a temporary file,
	 * this tempfile object is used to manage its lifetime.
	 */
	struct tempfile tempfile;
} diff_temp[2];

typedef unsigned long (*sane_truncate_fn)(char *line, unsigned long len);

struct emit_callback {
	int color_diff;
	unsigned ws_rule;
	int blank_at_eof_in_preimage;
	int blank_at_eof_in_postimage;
	int lno_in_preimage;
	int lno_in_postimage;
	sane_truncate_fn truncate;
	const char **label_path;
	struct diff_words_data *diff_words;
	struct diff_options *opt;
	struct strbuf *header;
};

static int count_lines(const char *data, int size)
{
	int count, ch, completely_empty = 1, nl_just_seen = 0;
	count = 0;
	while (0 < size--) {
		ch = *data++;
		if (ch == '\n') {
			count++;
			nl_just_seen = 1;
			completely_empty = 0;
		}
		else {
			nl_just_seen = 0;
			completely_empty = 0;
		}
	}
	if (completely_empty)
		return 0;
	if (!nl_just_seen)
		count++; /* no trailing newline */
	return count;
}

static int fill_mmfile(mmfile_t *mf, struct diff_filespec *one)
{
	if (!DIFF_FILE_VALID(one)) {
		mf->ptr = (char *)""; /* does not matter */
		mf->size = 0;
		return 0;
	}
	else if (diff_populate_filespec(one, 0))
		return -1;

	mf->ptr = one->data;
	mf->size = one->size;
	return 0;
}

/* like fill_mmfile, but only for size, so we can avoid retrieving blob */
static unsigned long diff_filespec_size(struct diff_filespec *one)
{
	if (!DIFF_FILE_VALID(one))
		return 0;
	diff_populate_filespec(one, CHECK_SIZE_ONLY);
	return one->size;
}

static int count_trailing_blank(mmfile_t *mf, unsigned ws_rule)
{
	char *ptr = mf->ptr;
	long size = mf->size;
	int cnt = 0;

	if (!size)
		return cnt;
	ptr += size - 1; /* pointing at the very end */
	if (*ptr != '\n')
		; /* incomplete line */
	else
		ptr--; /* skip the last LF */
	while (mf->ptr < ptr) {
		char *prev_eol;
		for (prev_eol = ptr; mf->ptr <= prev_eol; prev_eol--)
			if (*prev_eol == '\n')
				break;
		if (!ws_blank_line(prev_eol + 1, ptr - prev_eol, ws_rule))
			break;
		cnt++;
		ptr = prev_eol - 1;
	}
	return cnt;
}

static void check_blank_at_eof(mmfile_t *mf1, mmfile_t *mf2,
			       struct emit_callback *ecbdata)
{
	int l1, l2, at;
	unsigned ws_rule = ecbdata->ws_rule;
	l1 = count_trailing_blank(mf1, ws_rule);
	l2 = count_trailing_blank(mf2, ws_rule);
	if (l2 <= l1) {
		ecbdata->blank_at_eof_in_preimage = 0;
		ecbdata->blank_at_eof_in_postimage = 0;
		return;
	}
	at = count_lines(mf1->ptr, mf1->size);
	ecbdata->blank_at_eof_in_preimage = (at - l1) + 1;

	at = count_lines(mf2->ptr, mf2->size);
	ecbdata->blank_at_eof_in_postimage = (at - l2) + 1;
}

static void emit_line_0(struct diff_options *o, const char *set, const char *reset,
			int first, const char *line, int len)
{
	int has_trailing_newline, has_trailing_carriage_return;
	int nofirst;
	FILE *file = o->file;

	fputs(diff_line_prefix(o), file);

	if (len == 0) {
		has_trailing_newline = (first == '\n');
		has_trailing_carriage_return = (!has_trailing_newline &&
						(first == '\r'));
		nofirst = has_trailing_newline || has_trailing_carriage_return;
	} else {
		has_trailing_newline = (len > 0 && line[len-1] == '\n');
		if (has_trailing_newline)
			len--;
		has_trailing_carriage_return = (len > 0 && line[len-1] == '\r');
		if (has_trailing_carriage_return)
			len--;
		nofirst = 0;
	}

	if (len || !nofirst) {
		fputs(set, file);
		if (!nofirst)
			fputc(first, file);
		fwrite(line, len, 1, file);
		fputs(reset, file);
	}
	if (has_trailing_carriage_return)
		fputc('\r', file);
	if (has_trailing_newline)
		fputc('\n', file);
}

static void emit_line(struct diff_options *o, const char *set, const char *reset,
		      const char *line, int len)
{
	emit_line_0(o, set, reset, line[0], line+1, len-1);
}

static int new_blank_line_at_eof(struct emit_callback *ecbdata, const char *line, int len)
{
	if (!((ecbdata->ws_rule & WS_BLANK_AT_EOF) &&
	      ecbdata->blank_at_eof_in_preimage &&
	      ecbdata->blank_at_eof_in_postimage &&
	      ecbdata->blank_at_eof_in_preimage <= ecbdata->lno_in_preimage &&
	      ecbdata->blank_at_eof_in_postimage <= ecbdata->lno_in_postimage))
		return 0;
	return ws_blank_line(line, len, ecbdata->ws_rule);
}

static void emit_line_checked(const char *reset,
			      struct emit_callback *ecbdata,
			      const char *line, int len,
			      enum color_diff color,
			      unsigned ws_error_highlight,
			      char sign)
{
	const char *set = diff_get_color(ecbdata->color_diff, color);
	const char *ws = NULL;

	if (ecbdata->opt->ws_error_highlight & ws_error_highlight) {
		ws = diff_get_color(ecbdata->color_diff, DIFF_WHITESPACE);
		if (!*ws)
			ws = NULL;
	}

	if (!ws)
		emit_line_0(ecbdata->opt, set, reset, sign, line, len);
	else if (sign == '+' && new_blank_line_at_eof(ecbdata, line, len))
		/* Blank line at EOF - paint '+' as well */
		emit_line_0(ecbdata->opt, ws, reset, sign, line, len);
	else {
		/* Emit just the prefix, then the rest. */
		emit_line_0(ecbdata->opt, set, reset, sign, "", 0);
		ws_check_emit(line, len, ecbdata->ws_rule,
			      ecbdata->opt->file, set, reset, ws);
	}
}

static void emit_add_line(const char *reset,
			  struct emit_callback *ecbdata,
			  const char *line, int len)
{
	emit_line_checked(reset, ecbdata, line, len,
			  DIFF_FILE_NEW, WSEH_NEW, '+');
}

static void emit_del_line(const char *reset,
			  struct emit_callback *ecbdata,
			  const char *line, int len)
{
	emit_line_checked(reset, ecbdata, line, len,
			  DIFF_FILE_OLD, WSEH_OLD, '-');
}

static void emit_context_line(const char *reset,
			      struct emit_callback *ecbdata,
			      const char *line, int len)
{
	emit_line_checked(reset, ecbdata, line, len,
			  DIFF_CONTEXT, WSEH_CONTEXT, ' ');
}

static void emit_hunk_header(struct emit_callback *ecbdata,
			     const char *line, int len)
{
	const char *context = diff_get_color(ecbdata->color_diff, DIFF_CONTEXT);
	const char *frag = diff_get_color(ecbdata->color_diff, DIFF_FRAGINFO);
	const char *func = diff_get_color(ecbdata->color_diff, DIFF_FUNCINFO);
	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
	static const char atat[2] = { '@', '@' };
	const char *cp, *ep;
	struct strbuf msgbuf = STRBUF_INIT;
	int org_len = len;
	int i = 1;

	/*
	 * As a hunk header must begin with "@@ -<old>, +<new> @@",
	 * it always is at least 10 bytes long.
	 */
	if (len < 10 ||
	    memcmp(line, atat, 2) ||
	    !(ep = memmem(line + 2, len - 2, atat, 2))) {
		emit_line(ecbdata->opt, context, reset, line, len);
		return;
	}
	ep += 2; /* skip over @@ */

	/* The hunk header in fraginfo color */
	strbuf_addstr(&msgbuf, frag);
	strbuf_add(&msgbuf, line, ep - line);
	strbuf_addstr(&msgbuf, reset);

	/*
	 * trailing "\r\n"
	 */
	for ( ; i < 3; i++)
		if (line[len - i] == '\r' || line[len - i] == '\n')
			len--;

	/* blank before the func header */
	for (cp = ep; ep - line < len; ep++)
		if (*ep != ' ' && *ep != '\t')
			break;
	if (ep != cp) {
		strbuf_addstr(&msgbuf, context);
		strbuf_add(&msgbuf, cp, ep - cp);
		strbuf_addstr(&msgbuf, reset);
	}

	if (ep < line + len) {
		strbuf_addstr(&msgbuf, func);
		strbuf_add(&msgbuf, ep, line + len - ep);
		strbuf_addstr(&msgbuf, reset);
	}

	strbuf_add(&msgbuf, line + len, org_len - len);
	emit_line(ecbdata->opt, "", "", msgbuf.buf, msgbuf.len);
	strbuf_release(&msgbuf);
}

static struct diff_tempfile *claim_diff_tempfile(void) {
	int i;
	for (i = 0; i < ARRAY_SIZE(diff_temp); i++)
		if (!diff_temp[i].name)
			return diff_temp + i;
	die("BUG: diff is failing to clean up its tempfiles");
}

static void remove_tempfile(void)
{
	int i;
	for (i = 0; i < ARRAY_SIZE(diff_temp); i++) {
		if (is_tempfile_active(&diff_temp[i].tempfile))
			delete_tempfile(&diff_temp[i].tempfile);
		diff_temp[i].name = NULL;
	}
}

static void print_line_count(FILE *file, int count)
{
	switch (count) {
	case 0:
		fprintf(file, "0,0");
		break;
	case 1:
		fprintf(file, "1");
		break;
	default:
		fprintf(file, "1,%d", count);
		break;
	}
}

static void emit_rewrite_lines(struct emit_callback *ecb,
			       int prefix, const char *data, int size)
{
	const char *endp = NULL;
	static const char *nneof = " No newline at end of file\n";
	const char *reset = diff_get_color(ecb->color_diff, DIFF_RESET);

	while (0 < size) {
		int len;

		endp = memchr(data, '\n', size);
		len = endp ? (endp - data + 1) : size;
		if (prefix != '+') {
			ecb->lno_in_preimage++;
			emit_del_line(reset, ecb, data, len);
		} else {
			ecb->lno_in_postimage++;
			emit_add_line(reset, ecb, data, len);
		}
		size -= len;
		data += len;
	}
	if (!endp) {
		const char *context = diff_get_color(ecb->color_diff,
						     DIFF_CONTEXT);
		putc('\n', ecb->opt->file);
		emit_line_0(ecb->opt, context, reset, '\\',
			    nneof, strlen(nneof));
	}
}

static void emit_rewrite_diff(const char *name_a,
			      const char *name_b,
			      struct diff_filespec *one,
			      struct diff_filespec *two,
			      struct userdiff_driver *textconv_one,
			      struct userdiff_driver *textconv_two,
			      struct diff_options *o)
{
	int lc_a, lc_b;
	const char *name_a_tab, *name_b_tab;
	const char *metainfo = diff_get_color(o->use_color, DIFF_METAINFO);
	const char *fraginfo = diff_get_color(o->use_color, DIFF_FRAGINFO);
	const char *reset = diff_get_color(o->use_color, DIFF_RESET);
	static struct strbuf a_name = STRBUF_INIT, b_name = STRBUF_INIT;
	const char *a_prefix, *b_prefix;
	char *data_one, *data_two;
	size_t size_one, size_two;
	struct emit_callback ecbdata;
	const char *line_prefix = diff_line_prefix(o);

	if (diff_mnemonic_prefix && DIFF_OPT_TST(o, REVERSE_DIFF)) {
		a_prefix = o->b_prefix;
		b_prefix = o->a_prefix;
	} else {
		a_prefix = o->a_prefix;
		b_prefix = o->b_prefix;
	}

	name_a += (*name_a == '/');
	name_b += (*name_b == '/');
	name_a_tab = strchr(name_a, ' ') ? "\t" : "";
	name_b_tab = strchr(name_b, ' ') ? "\t" : "";

	strbuf_reset(&a_name);
	strbuf_reset(&b_name);
	quote_two_c_style(&a_name, a_prefix, name_a, 0);
	quote_two_c_style(&b_name, b_prefix, name_b, 0);

	size_one = fill_textconv(textconv_one, one, &data_one);
	size_two = fill_textconv(textconv_two, two, &data_two);

	memset(&ecbdata, 0, sizeof(ecbdata));
	ecbdata.color_diff = want_color(o->use_color);
	ecbdata.ws_rule = whitespace_rule(name_b);
	ecbdata.opt = o;
	if (ecbdata.ws_rule & WS_BLANK_AT_EOF) {
		mmfile_t mf1, mf2;
		mf1.ptr = (char *)data_one;
		mf2.ptr = (char *)data_two;
		mf1.size = size_one;
		mf2.size = size_two;
		check_blank_at_eof(&mf1, &mf2, &ecbdata);
	}
	ecbdata.lno_in_preimage = 1;
	ecbdata.lno_in_postimage = 1;

	lc_a = count_lines(data_one, size_one);
	lc_b = count_lines(data_two, size_two);
	fprintf(o->file,
		"%s%s--- %s%s%s\n%s%s+++ %s%s%s\n%s%s@@ -",
		line_prefix, metainfo, a_name.buf, name_a_tab, reset,
		line_prefix, metainfo, b_name.buf, name_b_tab, reset,
		line_prefix, fraginfo);
	if (!o->irreversible_delete)
		print_line_count(o->file, lc_a);
	else
		fprintf(o->file, "?,?");
	fprintf(o->file, " +");
	print_line_count(o->file, lc_b);
	fprintf(o->file, " @@%s\n", reset);
	if (lc_a && !o->irreversible_delete)
		emit_rewrite_lines(&ecbdata, '-', data_one, size_one);
	if (lc_b)
		emit_rewrite_lines(&ecbdata, '+', data_two, size_two);
	if (textconv_one)
		free((char *)data_one);
	if (textconv_two)
		free((char *)data_two);
}

struct diff_words_buffer {
	mmfile_t text;
	long alloc;
	struct diff_words_orig {
		const char *begin, *end;
	} *orig;
	int orig_nr, orig_alloc;
};

static void diff_words_append(char *line, unsigned long len,
		struct diff_words_buffer *buffer)
{
	ALLOC_GROW(buffer->text.ptr, buffer->text.size + len, buffer->alloc);
	line++;
	len--;
	memcpy(buffer->text.ptr + buffer->text.size, line, len);
	buffer->text.size += len;
	buffer->text.ptr[buffer->text.size] = '\0';
}

struct diff_words_style_elem {
	const char *prefix;
	const char *suffix;
	const char *color; /* NULL; filled in by the setup code if
			    * color is enabled */
};

struct diff_words_style {
	enum diff_words_type type;
	struct diff_words_style_elem new, old, ctx;
	const char *newline;
};

static struct diff_words_style diff_words_styles[] = {
	{ DIFF_WORDS_PORCELAIN, {"+", "\n"}, {"-", "\n"}, {" ", "\n"}, "~\n" },
	{ DIFF_WORDS_PLAIN, {"{+", "+}"}, {"[-", "-]"}, {"", ""}, "\n" },
	{ DIFF_WORDS_COLOR, {"", ""}, {"", ""}, {"", ""}, "\n" }
};

struct diff_words_data {
	struct diff_words_buffer minus, plus;
	const char *current_plus;
	int last_minus;
	struct diff_options *opt;
	regex_t *word_regex;
	enum diff_words_type type;
	struct diff_words_style *style;
};

static int fn_out_diff_words_write_helper(FILE *fp,
					  struct diff_words_style_elem *st_el,
					  const char *newline,
					  size_t count, const char *buf,
					  const char *line_prefix)
{
	int print = 0;

	while (count) {
		char *p = memchr(buf, '\n', count);
		if (print)
			fputs(line_prefix, fp);
		if (p != buf) {
			if (st_el->color && fputs(st_el->color, fp) < 0)
				return -1;
			if (fputs(st_el->prefix, fp) < 0 ||
			    fwrite(buf, p ? p - buf : count, 1, fp) != 1 ||
			    fputs(st_el->suffix, fp) < 0)
				return -1;
			if (st_el->color && *st_el->color
			    && fputs(GIT_COLOR_RESET, fp) < 0)
				return -1;
		}
		if (!p)
			return 0;
		if (fputs(newline, fp) < 0)
			return -1;
		count -= p + 1 - buf;
		buf = p + 1;
		print = 1;
	}
	return 0;
}

/*
 * '--color-words' algorithm can be described as:
 *
 *   1. collect the minus/plus lines of a diff hunk, divided into
 *      minus-lines and plus-lines;
 *
 *   2. break both minus-lines and plus-lines into words and
 *      place them into two mmfile_t with one word for each line;
 *
 *   3. use xdiff to run diff on the two mmfile_t to get the words level diff;
 *
 * And for the common parts of the both file, we output the plus side text.
 * diff_words->current_plus is used to trace the current position of the plus file
 * which printed. diff_words->last_minus is used to trace the last minus word
 * printed.
 *
 * For '--graph' to work with '--color-words', we need to output the graph prefix
 * on each line of color words output. Generally, there are two conditions on
 * which we should output the prefix.
 *
 *   1. diff_words->last_minus == 0 &&
 *      diff_words->current_plus == diff_words->plus.text.ptr
 *
 *      that is: the plus text must start as a new line, and if there is no minus
 *      word printed, a graph prefix must be printed.
 *
 *   2. diff_words->current_plus > diff_words->plus.text.ptr &&
 *      *(diff_words->current_plus - 1) == '\n'
 *
 *      that is: a graph prefix must be printed following a '\n'
 */
static int color_words_output_graph_prefix(struct diff_words_data *diff_words)
{
	if ((diff_words->last_minus == 0 &&
		diff_words->current_plus == diff_words->plus.text.ptr) ||
		(diff_words->current_plus > diff_words->plus.text.ptr &&
		*(diff_words->current_plus - 1) == '\n')) {
		return 1;
	} else {
		return 0;
	}
}

static void fn_out_diff_words_aux(void *priv, char *line, unsigned long len)
{
	struct diff_words_data *diff_words = priv;
	struct diff_words_style *style = diff_words->style;
	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;
	const char *line_prefix;

	if (line[0] != '@' || parse_hunk_header(line, len,
			&minus_first, &minus_len, &plus_first, &plus_len))
		return;

	assert(opt);
	line_prefix = diff_line_prefix(opt);

	/* POSIX requires that first be decremented by one if len == 0... */
	if (minus_len) {
		minus_begin = diff_words->minus.orig[minus_first].begin;
		minus_end =
			diff_words->minus.orig[minus_first + minus_len - 1].end;
	} else
		minus_begin = minus_end =
			diff_words->minus.orig[minus_first].end;

	if (plus_len) {
		plus_begin = diff_words->plus.orig[plus_first].begin;
		plus_end = diff_words->plus.orig[plus_first + plus_len - 1].end;
	} else
		plus_begin = plus_end = diff_words->plus.orig[plus_first].end;

	if (color_words_output_graph_prefix(diff_words)) {
		fputs(line_prefix, diff_words->opt->file);
	}
	if (diff_words->current_plus != plus_begin) {
		fn_out_diff_words_write_helper(diff_words->opt->file,
				&style->ctx, style->newline,
				plus_begin - diff_words->current_plus,
				diff_words->current_plus, line_prefix);
		if (*(plus_begin - 1) == '\n')
			fputs(line_prefix, diff_words->opt->file);
	}
	if (minus_begin != minus_end) {
		fn_out_diff_words_write_helper(diff_words->opt->file,
				&style->old, style->newline,
				minus_end - minus_begin, minus_begin,
				line_prefix);
	}
	if (plus_begin != plus_end) {
		fn_out_diff_words_write_helper(diff_words->opt->file,
				&style->new, style->newline,
				plus_end - plus_begin, plus_begin,
				line_prefix);
	}

	diff_words->current_plus = plus_end;
	diff_words->last_minus = minus_first;
}

/* This function starts looking at *begin, and returns 0 iff a word was found. */
static int find_word_boundaries(mmfile_t *buffer, regex_t *word_regex,
		int *begin, int *end)
{
	if (word_regex && *begin < buffer->size) {
		regmatch_t match[1];
		if (!regexec_buf(word_regex, buffer->ptr + *begin,
				 buffer->size - *begin, 1, match, 0)) {
			char *p = memchr(buffer->ptr + *begin + match[0].rm_so,
					'\n', match[0].rm_eo - match[0].rm_so);
			*end = p ? p - buffer->ptr : match[0].rm_eo + *begin;
			*begin += match[0].rm_so;
			return *begin >= *end;
		}
		return -1;
	}

	/* find the next word */
	while (*begin < buffer->size && isspace(buffer->ptr[*begin]))
		(*begin)++;
	if (*begin >= buffer->size)
		return -1;

	/* find the end of the word */
	*end = *begin + 1;
	while (*end < buffer->size && !isspace(buffer->ptr[*end]))
		(*end)++;

	return 0;
}

/*
 * This function splits the words in buffer->text, stores the list with
 * newline separator into out, and saves the offsets of the original words
 * in buffer->orig.
 */
static void diff_words_fill(struct diff_words_buffer *buffer, mmfile_t *out,
		regex_t *word_regex)
{
	int i, j;
	long alloc = 0;

	out->size = 0;
	out->ptr = NULL;

	/* fake an empty "0th" word */
	ALLOC_GROW(buffer->orig, 1, buffer->orig_alloc);
	buffer->orig[0].begin = buffer->orig[0].end = buffer->text.ptr;
	buffer->orig_nr = 1;

	for (i = 0; i < buffer->text.size; i++) {
		if (find_word_boundaries(&buffer->text, word_regex, &i, &j))
			return;

		/* store original boundaries */
		ALLOC_GROW(buffer->orig, buffer->orig_nr + 1,
				buffer->orig_alloc);
		buffer->orig[buffer->orig_nr].begin = buffer->text.ptr + i;
		buffer->orig[buffer->orig_nr].end = buffer->text.ptr + j;
		buffer->orig_nr++;

		/* store one word */
		ALLOC_GROW(out->ptr, out->size + j - i + 1, alloc);
		memcpy(out->ptr + out->size, buffer->text.ptr + i, j - i);
		out->ptr[out->size + j - i] = '\n';
		out->size += j - i + 1;

		i = j - 1;
	}
}

/* this executes the word diff on the accumulated buffers */
static void diff_words_show(struct diff_words_data *diff_words)
{
	xpparam_t xpp;
	xdemitconf_t xecfg;
	mmfile_t minus, plus;
	struct diff_words_style *style = diff_words->style;

	struct diff_options *opt = diff_words->opt;
	const char *line_prefix;

	assert(opt);
	line_prefix = diff_line_prefix(opt);

	/* special case: only removal */
	if (!diff_words->plus.text.size) {
		fputs(line_prefix, diff_words->opt->file);
		fn_out_diff_words_write_helper(diff_words->opt->file,
			&style->old, style->newline,
			diff_words->minus.text.size,
			diff_words->minus.text.ptr, line_prefix);
		diff_words->minus.text.size = 0;
		return;
	}

	diff_words->current_plus = diff_words->plus.text.ptr;
	diff_words->last_minus = 0;

	memset(&xpp, 0, sizeof(xpp));
	memset(&xecfg, 0, sizeof(xecfg));
	diff_words_fill(&diff_words->minus, &minus, diff_words->word_regex);
	diff_words_fill(&diff_words->plus, &plus, diff_words->word_regex);
	xpp.flags = 0;
	/* as only the hunk header will be parsed, we need a 0-context */
	xecfg.ctxlen = 0;
	if (xdi_diff_outf(&minus, &plus, fn_out_diff_words_aux, diff_words,
			  &xpp, &xecfg))
		die("unable to generate word diff");
	free(minus.ptr);
	free(plus.ptr);
	if (diff_words->current_plus != diff_words->plus.text.ptr +
			diff_words->plus.text.size) {
		if (color_words_output_graph_prefix(diff_words))
			fputs(line_prefix, diff_words->opt->file);
		fn_out_diff_words_write_helper(diff_words->opt->file,
			&style->ctx, style->newline,
			diff_words->plus.text.ptr + diff_words->plus.text.size
			- diff_words->current_plus, diff_words->current_plus,
			line_prefix);
	}
	diff_words->minus.text.size = diff_words->plus.text.size = 0;
}

/* In "color-words" mode, show word-diff of words accumulated in the buffer */
static void diff_words_flush(struct emit_callback *ecbdata)
{
	if (ecbdata->diff_words->minus.text.size ||
	    ecbdata->diff_words->plus.text.size)
		diff_words_show(ecbdata->diff_words);
}

static void diff_filespec_load_driver(struct diff_filespec *one)
{
	/* Use already-loaded driver */
	if (one->driver)
		return;

	if (S_ISREG(one->mode))
		one->driver = userdiff_find_by_path(one->path);

	/* Fallback to default settings */
	if (!one->driver)
		one->driver = userdiff_find_by_name("default");
}

static const char *userdiff_word_regex(struct diff_filespec *one)
{
	diff_filespec_load_driver(one);
	return one->driver->word_regex;
}

static void init_diff_words_data(struct emit_callback *ecbdata,
				 struct diff_options *orig_opts,
				 struct diff_filespec *one,
				 struct diff_filespec *two)
{
	int i;
	struct diff_options *o = xmalloc(sizeof(struct diff_options));
	memcpy(o, orig_opts, sizeof(struct diff_options));

	ecbdata->diff_words =
		xcalloc(1, sizeof(struct diff_words_data));
	ecbdata->diff_words->type = o->word_diff;
	ecbdata->diff_words->opt = o;
	if (!o->word_regex)
		o->word_regex = userdiff_word_regex(one);
	if (!o->word_regex)
		o->word_regex = userdiff_word_regex(two);
	if (!o->word_regex)
		o->word_regex = diff_word_regex_cfg;
	if (o->word_regex) {
		ecbdata->diff_words->word_regex = (regex_t *)
			xmalloc(sizeof(regex_t));
		if (regcomp(ecbdata->diff_words->word_regex,
			    o->word_regex,
			    REG_EXTENDED | REG_NEWLINE))
			die ("Invalid regular expression: %s",
			     o->word_regex);
	}
	for (i = 0; i < ARRAY_SIZE(diff_words_styles); i++) {
		if (o->word_diff == diff_words_styles[i].type) {
			ecbdata->diff_words->style =
				&diff_words_styles[i];
			break;
		}
	}
	if (want_color(o->use_color)) {
		struct diff_words_style *st = ecbdata->diff_words->style;
		st->old.color = diff_get_color_opt(o, DIFF_FILE_OLD);
		st->new.color = diff_get_color_opt(o, DIFF_FILE_NEW);
		st->ctx.color = diff_get_color_opt(o, DIFF_CONTEXT);
	}
}

static void free_diff_words_data(struct emit_callback *ecbdata)
{
	if (ecbdata->diff_words) {
		diff_words_flush(ecbdata);
		free (ecbdata->diff_words->opt);
		free (ecbdata->diff_words->minus.text.ptr);
		free (ecbdata->diff_words->minus.orig);
		free (ecbdata->diff_words->plus.text.ptr);
		free (ecbdata->diff_words->plus.orig);
		if (ecbdata->diff_words->word_regex) {
			regfree(ecbdata->diff_words->word_regex);
			free(ecbdata->diff_words->word_regex);
		}
		FREE_AND_NULL(ecbdata->diff_words);
	}
}

const char *diff_get_color(int diff_use_color, enum color_diff ix)
{
	if (want_color(diff_use_color))
		return diff_colors[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;
	unsigned long allot;
	size_t l = len;

	if (ecb->truncate)
		return ecb->truncate(line, len);
	cp = line;
	allot = l;
	while (0 < l) {
		(void) utf8_width(&cp, &l);
		if (!cp)
			break; /* truncated in the middle? */
	}
	return allot - l;
}

static void find_lno(const char *line, struct emit_callback *ecbdata)
{
	const char *p;
	ecbdata->lno_in_preimage = 0;
	ecbdata->lno_in_postimage = 0;
	p = strchr(line, '-');
	if (!p)
		return; /* cannot happen */
	ecbdata->lno_in_preimage = strtol(p + 1, NULL, 10);
	p = strchr(p, '+');
	if (!p)
		return; /* cannot happen */
	ecbdata->lno_in_postimage = strtol(p + 1, NULL, 10);
}

static void fn_out_consume(void *priv, char *line, unsigned long len)
{
	struct emit_callback *ecbdata = priv;
	const char *meta = diff_get_color(ecbdata->color_diff, DIFF_METAINFO);
	const char *context = diff_get_color(ecbdata->color_diff, DIFF_CONTEXT);
	const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
	struct diff_options *o = ecbdata->opt;
	const char *line_prefix = diff_line_prefix(o);

	o->found_changes = 1;

	if (ecbdata->header) {
		fprintf(o->file, "%s", ecbdata->header->buf);
		strbuf_reset(ecbdata->header);
		ecbdata->header = NULL;
	}

	if (ecbdata->label_path[0]) {
		const char *name_a_tab, *name_b_tab;

		name_a_tab = strchr(ecbdata->label_path[0], ' ') ? "\t" : "";
		name_b_tab = strchr(ecbdata->label_path[1], ' ') ? "\t" : "";

		fprintf(o->file, "%s%s--- %s%s%s\n",
			line_prefix, meta, ecbdata->label_path[0], reset, name_a_tab);
		fprintf(o->file, "%s%s+++ %s%s%s\n",
			line_prefix, meta, ecbdata->label_path[1], reset, name_b_tab);
		ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
	}

	if (diff_suppress_blank_empty
	    && len == 2 && line[0] == ' ' && line[1] == '\n') {
		line[0] = '\n';
		len = 1;
	}

	if (line[0] == '@') {
		if (ecbdata->diff_words)
			diff_words_flush(ecbdata);
		len = sane_truncate_line(ecbdata, line, len);
		find_lno(line, ecbdata);
		emit_hunk_header(ecbdata, line, len);
		if (line[len-1] != '\n')
			putc('\n', o->file);
		return;
	}

	if (ecbdata->diff_words) {
		if (line[0] == '-') {
			diff_words_append(line, len,
					  &ecbdata->diff_words->minus);
			return;
		} else if (line[0] == '+') {
			diff_words_append(line, len,
					  &ecbdata->diff_words->plus);
			return;
		} else if (starts_with(line, "\\ ")) {
			/*
			 * Eat the "no newline at eof" marker as if we
			 * saw a "+" or "-" line with nothing on it,
			 * and return without diff_words_flush() to
			 * defer processing. If this is the end of
			 * preimage, more "+" lines may come after it.
			 */
			return;
		}
		diff_words_flush(ecbdata);
		if (ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN) {
			emit_line(o, context, reset, line, len);
			fputs("~\n", o->file);
		} else {
			/*
			 * Skip the prefix character, if any.  With
			 * diff_suppress_blank_empty, there may be
			 * none.
			 */
			if (line[0] != '\n') {
			      line++;
			      len--;
			}
			emit_line(o, context, reset, line, len);
		}
		return;
	}

	switch (line[0]) {
	case '+':
		ecbdata->lno_in_postimage++;
		emit_add_line(reset, ecbdata, line + 1, len - 1);
		break;
	case '-':
		ecbdata->lno_in_preimage++;
		emit_del_line(reset, ecbdata, line + 1, len - 1);
		break;
	case ' ':
		ecbdata->lno_in_postimage++;
		ecbdata->lno_in_preimage++;
		emit_context_line(reset, ecbdata, line + 1, len - 1);
		break;
	default:
		/* incomplete line at the end */
		ecbdata->lno_in_preimage++;
		emit_line(o, diff_get_color(ecbdata->color_diff, DIFF_CONTEXT),
			  reset, line, len);
		break;
	}
}

static char *pprint_rename(const char *a, const char *b)
{
	const char *old = a;
	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;
	int qlen_a = quote_c_style(a, NULL, NULL, 0);
	int qlen_b = quote_c_style(b, NULL, NULL, 0);

	if (qlen_a || qlen_b) {
		quote_c_style(a, &name, NULL, 0);
		strbuf_addstr(&name, " => ");
		quote_c_style(b, &name, NULL, 0);
		return strbuf_detach(&name, NULL);
	}

	/* Find common prefix */
	pfx_length = 0;
	while (*old && *new && *old == *new) {
		if (*old == '/')
			pfx_length = old - a + 1;
		old++;
		new++;
	}

	/* Find common suffix */
	old = a + len_a;
	new = b + len_b;
	sfx_length = 0;
	/*
	 * 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--;
		new--;
	}

	/*
	 * pfx{mid-a => mid-b}sfx
	 * {pfx-a => pfx-b}sfx
	 * pfx{sfx-a => sfx-b}
	 * name-a => name-b
	 */
	a_midlen = len_a - pfx_length - sfx_length;
	b_midlen = len_b - pfx_length - sfx_length;
	if (a_midlen < 0)
		a_midlen = 0;
	if (b_midlen < 0)
		b_midlen = 0;

	strbuf_grow(&name, pfx_length + a_midlen + b_midlen + sfx_length + 7);
	if (pfx_length + sfx_length) {
		strbuf_add(&name, a, pfx_length);
		strbuf_addch(&name, '{');
	}
	strbuf_add(&name, a + pfx_length, a_midlen);
	strbuf_addstr(&name, " => ");
	strbuf_add(&name, b + pfx_length, b_midlen);
	if (pfx_length + sfx_length) {
		strbuf_addch(&name, '}');
		strbuf_add(&name, a + len_a - sfx_length, sfx_length);
	}
	return strbuf_detach(&name, NULL);
}

struct diffstat_t {
	int nr;
	int alloc;
	struct diffstat_file {
		char *from_name;
		char *name;
		char *print_name;
		unsigned is_unmerged:1;
		unsigned is_binary:1;
		unsigned is_renamed:1;
		unsigned is_interesting:1;
		uintmax_t added, deleted;
	} **files;
};

static struct diffstat_file *diffstat_add(struct diffstat_t *diffstat,
					  const char *name_a,
					  const char *name_b)
{
	struct diffstat_file *x;
	x = xcalloc(1, sizeof(*x));
	ALLOC_GROW(diffstat->files, diffstat->nr + 1, diffstat->alloc);
	diffstat->files[diffstat->nr++] = x;
	if (name_b) {
		x->from_name = xstrdup(name_a);
		x->name = xstrdup(name_b);
		x->is_renamed = 1;
	}
	else {
		x->from_name = NULL;
		x->name = xstrdup(name_a);
	}
	return x;
}

static void diffstat_consume(void *priv, char *line, unsigned long len)
{
	struct diffstat_t *diffstat = priv;
	struct diffstat_file *x = diffstat->files[diffstat->nr - 1];

	if (line[0] == '+')
		x->added++;
	else if (line[0] == '-')
		x->deleted++;
}

const char mime_boundary_leader[] = "------------";

static int scale_linear(int it, int width, int max_change)
{
	if (!it)
		return 0;
	/*
	 * make sure that at least one '-' or '+' is printed if
	 * there is any change to this path. The easiest way is to
	 * scale linearly as if the alloted width is one column shorter
	 * than it is, and then add 1 to the result.
	 */
	return 1 + (it * (width - 1) / max_change);
}

static void show_name(FILE *file,
		      const char *prefix, const char *name, int len)
{
	fprintf(file, " %s%-*s |", prefix, len, name);
}

static void show_graph(FILE *file, char ch, int cnt, const char *set, const char *reset)
{
	if (cnt <= 0)
		return;
	fprintf(file, "%s", set);
	while (cnt--)
		putc(ch, file);
	fprintf(file, "%s", reset);
}

static void fill_print_name(struct diffstat_file *file)
{
	char *pname;

	if (file->print_name)
		return;

	if (!file->is_renamed) {
		struct strbuf buf = STRBUF_INIT;
		if (quote_c_style(file->name, &buf, NULL, 0)) {
			pname = strbuf_detach(&buf, NULL);
		} else {
			pname = file->name;
			strbuf_release(&buf);
		}
	} else {
		pname = pprint_rename(file->from_name, file->name);
	}
	file->print_name = pname;
}

int print_stat_summary(FILE *fp, int files, int insertions, int deletions)
{
	struct strbuf sb = STRBUF_INIT;
	int ret;

	if (!files) {
		assert(insertions == 0 && deletions == 0);
		return fprintf(fp, "%s\n", " 0 files changed");
	}

	strbuf_addf(&sb,
		    (files == 1) ? " %d file changed" : " %d files changed",
		    files);

	/*
	 * For binary diff, the caller may want to print "x files
	 * changed" with insertions == 0 && deletions == 0.
	 *
	 * Not omitting "0 insertions(+), 0 deletions(-)" in this case
	 * is probably less confusing (i.e skip over "2 files changed
	 * but nothing about added/removed lines? Is this a bug in Git?").
	 */
	if (insertions || deletions == 0) {
		strbuf_addf(&sb,
			    (insertions == 1) ? ", %d insertion(+)" : ", %d insertions(+)",
			    insertions);
	}

	if (deletions || insertions == 0) {
		strbuf_addf(&sb,
			    (deletions == 1) ? ", %d deletion(-)" : ", %d deletions(-)",
			    deletions);
	}
	strbuf_addch(&sb, '\n');
	ret = fputs(sb.buf, fp);
	strbuf_release(&sb);
	return ret;
}

static void show_stats(struct diffstat_t *data, struct diff_options *options)
{
	int i, len, add, del, adds = 0, dels = 0;
	uintmax_t max_change = 0, max_len = 0;
	int total_files = data->nr, count;
	int width, name_width, graph_width, number_width = 0, bin_width = 0;
	const char *reset, *add_c, *del_c;
	const char *line_prefix = "";
	int extra_shown = 0;

	if (data->nr == 0)
		return;

	line_prefix = diff_line_prefix(options);
	count = options->stat_count ? options->stat_count : data->nr;

	reset = diff_get_color_opt(options, DIFF_RESET);
	add_c = diff_get_color_opt(options, DIFF_FILE_NEW);
	del_c = diff_get_color_opt(options, DIFF_FILE_OLD);

	/*
	 * Find the longest filename and max number of changes
	 */
	for (i = 0; (i < count) && (i < data->nr); i++) {
		struct diffstat_file *file = data->files[i];
		uintmax_t change = file->added + file->deleted;

		if (!file->is_interesting && (change == 0)) {
			count++; /* not shown == room for one more */
			continue;
		}
		fill_print_name(file);
		len = strlen(file->print_name);
		if (max_len < len)
			max_len = len;

		if (file->is_unmerged) {
			/* "Unmerged" is 8 characters */
			bin_width = bin_width < 8 ? 8 : bin_width;
			continue;
		}
		if (file->is_binary) {
			/* "Bin XXX -> YYY bytes" */
			int w = 14 + decimal_width(file->added)
				+ decimal_width(file->deleted);
			bin_width = bin_width < w ? w : bin_width;
			/* Display change counts aligned with "Bin" */
			number_width = 3;
			continue;
		}

		if (max_change < change)
			max_change = change;
	}
	count = i; /* where we can stop scanning in data->files[] */

	/*
	 * We have width = stat_width or term_columns() columns total.
	 * We want a maximum of min(max_len, stat_name_width) for the name part.
	 * We want a maximum of min(max_change, stat_graph_width) for the +- part.
	 * We also need 1 for " " and 4 + decimal_width(max_change)
	 * for " | NNNN " and one the empty column at the end, altogether
	 * 6 + decimal_width(max_change).
	 *
	 * If there's not enough space, we will use the smaller of
	 * stat_name_width (if set) and 5/8*width for the filename,
	 * and the rest for constant elements + graph part, but no more
	 * than stat_graph_width for the graph part.
	 * (5/8 gives 50 for filename and 30 for the constant parts + graph
	 * for the standard terminal size).
	 *
	 * In other words: stat_width limits the maximum width, and
	 * stat_name_width fixes the maximum width of the filename,
	 * and is also used to divide available columns if there
	 * aren't enough.
	 *
	 * Binary files are displayed with "Bin XXX -> YYY bytes"
	 * instead of the change count and graph. This part is treated
	 * similarly to the graph part, except that it is not
	 * "scaled". If total width is too small to accommodate the
	 * guaranteed minimum width of the filename part and the
	 * separators and this message, this message will "overflow"
	 * making the line longer than the maximum width.
	 */

	if (options->stat_width == -1)
		width = term_columns() - strlen(line_prefix);
	else
		width = options->stat_width ? options->stat_width : 80;
	number_width = decimal_width(max_change) > number_width ?
		decimal_width(max_change) : number_width;

	if (options->stat_graph_width == -1)
		options->stat_graph_width = diff_stat_graph_width;

	/*
	 * Guarantee 3/8*16==6 for the graph part
	 * and 5/8*16==10 for the filename part
	 */
	if (width < 16 + 6 + number_width)
		width = 16 + 6 + number_width;

	/*
	 * First assign sizes that are wanted, ignoring available width.
	 * strlen("Bin XXX -> YYY bytes") == bin_width, and the part
	 * starting from "XXX" should fit in graph_width.
	 */
	graph_width = max_change + 4 > bin_width ? max_change : bin_width - 4;
	if (options->stat_graph_width &&
	    options->stat_graph_width < graph_width)
		graph_width = options->stat_graph_width;

	name_width = (options->stat_name_width > 0 &&
		      options->stat_name_width < max_len) ?
		options->stat_name_width : max_len;

	/*
	 * Adjust adjustable widths not to exceed maximum width
	 */
	if (name_width + number_width + 6 + graph_width > width) {
		if (graph_width > width * 3/8 - number_width - 6) {
			graph_width = width * 3/8 - number_width - 6;
			if (graph_width < 6)
				graph_width = 6;
		}

		if (options->stat_graph_width &&
		    graph_width > options->stat_graph_width)
			graph_width = options->stat_graph_width;
		if (name_width > width - number_width - 6 - graph_width)
			name_width = width - number_width - 6 - graph_width;
		else
			graph_width = width - number_width - 6 - name_width;
	}

	/*
	 * From here name_width is the width of the name area,
	 * and graph_width is the width of the graph area.
	 * max_change is used to scale graph properly.
	 */
	for (i = 0; i < count; i++) {
		const char *prefix = "";
		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 (!file->is_interesting && (added + deleted == 0))
			continue;

		/*
		 * "scale" the filename
		 */
		len = name_width;
		name_len = strlen(name);
		if (name_width < name_len) {
			char *slash;
			prefix = "...";
			len -= 3;
			name += name_len - len;
			slash = strchr(name, '/');
			if (slash)
				name = slash;
		}

		if (file->is_binary) {
			fprintf(options->file, "%s", line_prefix);
			show_name(options->file, prefix, name, len);
			fprintf(options->file, " %*s", number_width, "Bin");
			if (!added && !deleted) {
				putc('\n', options->file);
				continue;
			}
			fprintf(options->file, " %s%"PRIuMAX"%s",
				del_c, deleted, reset);
			fprintf(options->file, " -> ");
			fprintf(options->file, "%s%"PRIuMAX"%s",
				add_c, added, reset);
			fprintf(options->file, " bytes");
			fprintf(options->file, "\n");
			continue;
		}
		else if (file->is_unmerged) {
			fprintf(options->file, "%s", line_prefix);
			show_name(options->file, prefix, name, len);
			fprintf(options->file, " Unmerged\n");
			continue;
		}

		/*
		 * scale the add/delete
		 */
		add = added;
		del = deleted;

		if (graph_width <= max_change) {
			int total = scale_linear(add + del, graph_width, max_change);
			if (total < 2 && add && del)
				/* width >= 2 due to the sanity check */
				total = 2;
			if (add < del) {
				add = scale_linear(add, graph_width, max_change);
				del = total - add;
			} else {
				del = scale_linear(del, graph_width, max_change);
				add = total - del;
			}
		}
		fprintf(options->file, "%s", line_prefix);
		show_name(options->file, prefix, name, len);
		fprintf(options->file, " %*"PRIuMAX"%s",
			number_width, added + deleted,
			added + deleted ? " " : "");
		show_graph(options->file, '+', add, add_c, reset);
		show_graph(options->file, '-', del, del_c, reset);
		fprintf(options->file, "\n");
	}

	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;
		}

		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;
	}
	fprintf(options->file, "%s", line_prefix);
	print_stat_summary(options->file, total_files, adds, dels);
}

static void show_shortstats(struct diffstat_t *data, struct diff_options *options)
{
	int i, adds = 0, dels = 0, total_files = data->nr;

	if (data->nr == 0)
		return;

	for (i = 0; i < data->nr; i++) {
		int added = data->files[i]->added;
		int deleted= data->files[i]->deleted;

		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;
		}
	}
	fprintf(options->file, "%s", diff_line_prefix(options));
	print_stat_summary(options->file, total_files, adds, dels);
}

static void show_numstat(struct diffstat_t *data, struct diff_options *options)
{
	int i;

	if (data->nr == 0)
		return;

	for (i = 0; i < data->nr; i++) {
		struct diffstat_file *file = data->files[i];

		fprintf(options->file, "%s", diff_line_prefix(options));

		if (file->is_binary)
			fprintf(options->file, "-\t-\t");
		else
			fprintf(options->file,
				"%"PRIuMAX"\t%"PRIuMAX"\t",
				file->added, file->deleted);
		if (options->line_termination) {
			fill_print_name(file);
			if (!file->is_renamed)
				write_name_quoted(file->name, options->file,
						  options->line_termination);
			else {
				fputs(file->print_name, options->file);
				putc(options->line_termination, options->file);
			}
		} else {
			if (file->is_renamed) {
				putc('\0', options->file);
				write_name_quoted(file->from_name, options->file, '\0');
			}
			write_name_quoted(file->name, options->file, '\0');
		}
	}
}

struct dirstat_file {
	const char *name;
	unsigned long changed;
};

struct dirstat_dir {
	struct dirstat_file *files;
	int alloc, nr, permille, cumulative;
};

static long gather_dirstat(struct diff_options *opt, struct dirstat_dir *dir,
		unsigned long changed, const char *base, int baselen)
{
	unsigned long this_dir = 0;
	unsigned int sources = 0;
	const char *line_prefix = diff_line_prefix(opt);

	while (dir->nr) {
		struct dirstat_file *f = dir->files;
		int namelen = strlen(f->name);
		unsigned long this;
		char *slash;

		if (namelen < baselen)
			break;
		if (memcmp(f->name, base, baselen))
			break;
		slash = strchr(f->name + baselen, '/');
		if (slash) {
			int newbaselen = slash + 1 - f->name;
			this = gather_dirstat(opt, dir, changed, f->name, newbaselen);
			sources++;
		} else {
			this = f->changed;
			dir->files++;
			dir->nr--;
			sources += 2;
		}
		this_dir += this;
	}

	/*
	 * We don't report dirstat's for
	 *  - the top level
	 *  - or cases where everything came from a single directory
	 *    under this directory (sources == 1).
	 */
	if (baselen && sources != 1) {
		if (this_dir) {
			int permille = this_dir * 1000 / changed;
			if (permille >= dir->permille) {
				fprintf(opt->file, "%s%4d.%01d%% %.*s\n", line_prefix,
					permille / 10, permille % 10, baselen, base);
				if (!dir->cumulative)
					return 0;
			}
		}
	}
	return this_dir;
}

static int dirstat_compare(const void *_a, const void *_b)
{
	const struct dirstat_file *a = _a;
	const struct dirstat_file *b = _b;
	return strcmp(a->name, b->name);
}

static void show_dirstat(struct diff_options *options)
{
	int i;
	unsigned long changed;
	struct dirstat_dir dir;
	struct diff_queue_struct *q = &diff_queued_diff;

	dir.files = NULL;
	dir.alloc = 0;
	dir.nr = 0;
	dir.permille = options->dirstat_permille;
	dir.cumulative = DIFF_OPT_TST(options, DIRSTAT_CUMULATIVE);

	changed = 0;
	for (i = 0; i < q->nr; i++) {
		struct diff_filepair *p = q->queue[i];
		const char *name;
		unsigned long copied, added, damage;
		int content_changed;

		name = p->two->path ? p->two->path : p->one->path;

		if (p->one->oid_valid && p->two->oid_valid)
			content_changed = oidcmp(&p->one->oid, &p->two->oid);
		else
			content_changed = 1;

		if (!content_changed) {
			/*
			 * The SHA1 has not changed, so pre-/post-content is
			 * identical. We can therefore skip looking at the
			 * file contents altogether.
			 */
			damage = 0;
			goto found_damage;
		}

		if (DIFF_OPT_TST(options, DIRSTAT_BY_FILE)) {
			/*
			 * In --dirstat-by-file mode, we don't really need to
			 * look at the actual file contents at all.
			 * The fact that the SHA1 changed is enough for us to
			 * add this file to the list of results
			 * (with each file contributing equal damage).
			 */
			damage = 1;
			goto found_damage;
		}

		if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
			diff_populate_filespec(p->one, 0);
			diff_populate_filespec(p->two, 0);
			diffcore_count_changes(p->one, p->two, NULL, NULL,
					       &copied, &added);
			diff_free_filespec_data(p->one);
			diff_free_filespec_data(p->two);
		} else if (DIFF_FILE_VALID(p->one)) {
			diff_populate_filespec(p->one, CHECK_SIZE_ONLY);
			copied = added = 0;
			diff_free_filespec_data(p->one);
		} else if (DIFF_FILE_VALID(p->two)) {
			diff_populate_filespec(p->two, CHECK_SIZE_ONLY);
			copied = 0;
			added = p->two->size;
			diff_free_filespec_data(p->two);
		} else
			continue;

		/*
		 * Original minus copied is the removed material,
		 * added is the new material.  They are both damages
		 * made to the preimage.
		 * If the resulting damage is zero, we know that
		 * diffcore_count_changes() considers the two entries to
		 * be identical, but since content_changed is true, we
		 * know that there must have been _some_ kind of change,
		 * so we force all entries to have damage > 0.
		 */
		damage = (p->one->size - copied) + added;
		if (!damage)
			damage = 1;

found_damage:
		ALLOC_GROW(dir.files, dir.nr + 1, dir.alloc);
		dir.files[dir.nr].name = name;
		dir.files[dir.nr].changed = damage;
		changed += damage;
		dir.nr++;
	}

	/* This can happen even with many files, if everything was renames */
	if (!changed)
		return;

	/* Show all directories with more than x% of the changes */
	QSORT(dir.files, dir.nr, dirstat_compare);
	gather_dirstat(options, &dir, changed, "", 0);
}

static void show_dirstat_by_line(struct diffstat_t *data, struct diff_options *options)
{
	int i;
	unsigned long changed;
	struct dirstat_dir dir;

	if (data->nr == 0)
		return;

	dir.files = NULL;
	dir.alloc = 0;
	dir.nr = 0;
	dir.permille = options->dirstat_permille;
	dir.cumulative = DIFF_OPT_TST(options, DIRSTAT_CUMULATIVE);

	changed = 0;
	for (i = 0; i < data->nr; i++) {
		struct diffstat_file *file = data->files[i];
		unsigned long damage = file->added + file->deleted;
		if (file->is_binary)
			/*
			 * binary files counts bytes, not lines. Must find some
			 * way to normalize binary bytes vs. textual lines.
			 * The following heuristic assumes that there are 64
			 * bytes per "line".
			 * This is stupid and ugly, but very cheap...
			 */
			damage = DIV_ROUND_UP(damage, 64);
		ALLOC_GROW(dir.files, dir.nr + 1, dir.alloc);
		dir.files[dir.nr].name = file->name;
		dir.files[dir.nr].changed = damage;
		changed += damage;
		dir.nr++;
	}

	/* This can happen even with many files, if everything was renames */
	if (!changed)
		return;

	/* Show all directories with more than x% of the changes */
	QSORT(dir.files, dir.nr, dirstat_compare);
	gather_dirstat(options, &dir, changed, "", 0);
}

static void free_diffstat_info(struct diffstat_t *diffstat)
{
	int i;
	for (i = 0; i < diffstat->nr; i++) {
		struct diffstat_file *f = diffstat->files[i];
		if (f->name != f->print_name)
			free(f->print_name);
		free(f->name);
		free(f->from_name);
		free(f);
	}
	free(diffstat->files);
}

struct checkdiff_t {
	const char *filename;
	int lineno;
	int conflict_marker_size;
	struct diff_options *o;
	unsigned ws_rule;
	unsigned status;
};

static int is_conflict_marker(const char *line, int marker_size, unsigned long len)
{
	char firstchar;
	int cnt;

	if (len < marker_size + 1)
		return 0;
	firstchar = line[0];
	switch (firstchar) {
	case '=': case '>': case '<': case '|':
		break;
	default:
		return 0;
	}
	for (cnt = 1; cnt < marker_size; cnt++)
		if (line[cnt] != firstchar)
			return 0;
	/* line[1] thru line[marker_size-1] are same as firstchar */
	if (len < marker_size + 1 || !isspace(line[marker_size]))
		return 0;
	return 1;
}

static void checkdiff_consume(void *priv, char *line, unsigned long len)
{
	struct checkdiff_t *data = priv;
	int marker_size = data->conflict_marker_size;
	const char *ws = diff_get_color(data->o->use_color, DIFF_WHITESPACE);
	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;
	const char *line_prefix;

	assert(data->o);
	line_prefix = diff_line_prefix(data->o);

	if (line[0] == '+') {
		unsigned bad;
		data->lineno++;
		if (is_conflict_marker(line + 1, marker_size, len - 1)) {
			data->status |= 1;
			fprintf(data->o->file,
				"%s%s:%d: leftover conflict marker\n",
				line_prefix, data->filename, data->lineno);
		}
		bad = ws_check(line + 1, len - 1, data->ws_rule);
		if (!bad)
			return;
		data->status |= bad;
		err = whitespace_error_string(bad);
		fprintf(data->o->file, "%s%s:%d: %s.\n",
			line_prefix, data->filename, data->lineno, err);
		free(err);
		emit_line(data->o, set, reset, line, 1);
		ws_check_emit(line + 1, len - 1, data->ws_rule,
			      data->o->file, set, reset, ws);
	} else if (line[0] == ' ') {
		data->lineno++;
	} else if (line[0] == '@') {
		char *plus = strchr(line, '+');
		if (plus)
			data->lineno = strtol(plus, NULL, 10) - 1;
		else
			die("invalid diff");
	}
}

static unsigned char *deflate_it(char *data,
				 unsigned long size,
				 unsigned long *result_size)
{
	int bound;
	unsigned char *deflated;
	git_zstream stream;

	git_deflate_init(&stream, zlib_compression_level);
	bound = git_deflate_bound(&stream, size);
	deflated = xmalloc(bound);
	stream.next_out = deflated;
	stream.avail_out = bound;

	stream.next_in = (unsigned char *)data;
	stream.avail_in = size;
	while (git_deflate(&stream, Z_FINISH) == Z_OK)
		; /* nothing */
	git_deflate_end(&stream);
	*result_size = stream.total_out;
	return deflated;
}

static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two,
				  const char *prefix)
{
	void *cp;
	void *delta;
	void *deflated;
	void *data;
	unsigned long orig_size;
	unsigned long delta_size;
	unsigned long deflate_size;
	unsigned long data_size;

	/* We could do deflated delta, or we could do just deflated two,
	 * whichever is smaller.
	 */
	delta = NULL;
	deflated = deflate_it(two->ptr, two->size, &deflate_size);
	if (one->size && two->size) {
		delta = diff_delta(one->ptr, one->size,
				   two->ptr, two->size,
				   &delta_size, deflate_size);
		if (delta) {
			void *to_free = delta;
			orig_size = delta_size;
			delta = deflate_it(delta, delta_size, &delta_size);
			free(to_free);
		}
	}

	if (delta && delta_size < deflate_size) {
		fprintf(file, "%sdelta %lu\n", prefix, orig_size);
		free(deflated);
		data = delta;
		data_size = delta_size;
	}
	else {
		fprintf(file, "%sliteral %lu\n", prefix, two->size);
		free(delta);
		data = deflated;
		data_size = deflate_size;
	}

	/* emit data encoded in base85 */
	cp = data;
	while (data_size) {
		int bytes = (52 < data_size) ? 52 : data_size;
		char line[70];
		data_size -= bytes;
		if (bytes <= 26)
			line[0] = bytes + 'A' - 1;
		else
			line[0] = bytes - 26 + 'a' - 1;
		encode_85(line + 1, cp, bytes);
		cp = (char *) cp + bytes;
		fprintf(file, "%s", prefix);
		fputs(line, file);
		fputc('\n', file);
	}
	fprintf(file, "%s\n", prefix);
	free(data);
}

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);
	emit_binary_diff_body(file, two, one, prefix);
}

int diff_filespec_is_binary(struct diff_filespec *one)
{
	if (one->is_binary == -1) {
		diff_filespec_load_driver(one);
		if (one->driver->binary != -1)
			one->is_binary = one->driver->binary;
		else {
			if (!one->data && DIFF_FILE_VALID(one))
				diff_populate_filespec(one, CHECK_BINARY);
			if (one->is_binary == -1 && one->data)
				one->is_binary = buffer_is_binary(one->data,
						one->size);
			if (one->is_binary == -1)
				one->is_binary = 0;
		}
	}
	return one->is_binary;
}

static const struct userdiff_funcname *diff_funcname_pattern(struct diff_filespec *one)
{
	diff_filespec_load_driver(one);
	return one->driver->funcname.pattern ? &one->driver->funcname : NULL;
}

void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b)
{
	if (!options->a_prefix)
		options->a_prefix = a;
	if (!options->b_prefix)
		options->b_prefix = b;
}

struct userdiff_driver *get_textconv(struct diff_filespec *one)
{
	if (!DIFF_FILE_VALID(one))
		return NULL;

	diff_filespec_load_driver(one);
	return userdiff_get_textconv(one->driver);
}

static void builtin_diff(const char *name_a,
			 const char *name_b,
			 struct diff_filespec *one,
			 struct diff_filespec *two,
			 const char *xfrm_msg,
			 int must_show_header,
			 struct diff_options *o,
			 int complete_rewrite)
{
	mmfile_t mf1, mf2;
	const char *lbl[2];
	char *a_one, *b_two;
	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;
	const char *line_prefix = diff_line_prefix(o);

	diff_set_mnemonic_prefix(o, "a/", "b/");
	if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
		a_prefix = o->b_prefix;
		b_prefix = o->a_prefix;
	} else {
		a_prefix = o->a_prefix;
		b_prefix = o->b_prefix;
	}

	if (o->submodule_format == DIFF_SUBMODULE_LOG &&
	    (!one->mode || S_ISGITLINK(one->mode)) &&
	    (!two->mode || S_ISGITLINK(two->mode))) {
		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
		show_submodule_summary(o->file, one->path ? one->path : two->path,
				line_prefix,
				&one->oid, &two->oid,
				two->dirty_submodule,
				meta, del, add, reset);
		return;
	} else if (o->submodule_format == DIFF_SUBMODULE_INLINE_DIFF &&
		   (!one->mode || S_ISGITLINK(one->mode)) &&
		   (!two->mode || S_ISGITLINK(two->mode))) {
		const char *del = diff_get_color_opt(o, DIFF_FILE_OLD);
		const char *add = diff_get_color_opt(o, DIFF_FILE_NEW);
		show_submodule_inline_diff(o->file, one->path ? one->path : two->path,
				line_prefix,
				&one->oid, &two->oid,
				two->dirty_submodule,
				meta, del, add, reset, o);
		return;
	}

	if (DIFF_OPT_TST(o, ALLOW_TEXTCONV)) {
		textconv_one = get_textconv(one);
		textconv_two = get_textconv(two);
	}

	/* Never use a non-valid filename anywhere if at all possible */
	name_a = DIFF_FILE_VALID(one) ? name_a : name_b;
	name_b = DIFF_FILE_VALID(two) ? name_b : name_a;

	a_one = quote_two(a_prefix, name_a + (*name_a == '/'));
	b_two = quote_two(b_pre