--- a/mercurial/thirdparty/xdiff/xdiff.h	Sat Mar 03 10:39:43 2018 -0800
+++ b/mercurial/thirdparty/xdiff/xdiff.h	Sat Mar 03 10:39:55 2018 -0800
@@ -27,6 +27,8 @@
 extern "C" {
 #endif /* #ifdef __cplusplus */
 
+#include <stddef.h> /* size_t */
+
 /* xpparm_t.flags */
 #define XDF_NEED_MINIMAL (1 << 0)
 
@@ -41,11 +43,6 @@
 
 #define XDF_IGNORE_BLANK_LINES (1 << 7)
 
-#define XDF_PATIENCE_DIFF (1 << 14)
-#define XDF_HISTOGRAM_DIFF (1 << 15)
-#define XDF_DIFF_ALGORITHM_MASK (XDF_PATIENCE_DIFF | XDF_HISTOGRAM_DIFF)
-#define XDF_DIFF_ALG(x) ((x) & XDF_DIFF_ALGORITHM_MASK)
-
 #define XDF_INDENT_HEURISTIC (1 << 23)
 
 /* xdemitconf_t.flags */

--- a/mercurial/thirdparty/xdiff/xdiffi.c	Sat Mar 03 10:39:43 2018 -0800
+++ b/mercurial/thirdparty/xdiff/xdiffi.c	Sat Mar 03 10:39:55 2018 -0800
@@ -328,12 +328,6 @@
 	xdalgoenv_t xenv;
 	diffdata_t dd1, dd2;
 
-	if (XDF_DIFF_ALG(xpp->flags) == XDF_PATIENCE_DIFF)
-		return xdl_do_patience_diff(mf1, mf2, xpp, xe);
-
-	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
-		return xdl_do_histogram_diff(mf1, mf2, xpp, xe);
-
 	if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
 
 		return -1;

--- a/mercurial/thirdparty/xdiff/xhistogram.c	Sat Mar 03 10:39:43 2018 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,363 +0,0 @@
-/*
- * Copyright (C) 2010, Google Inc.
- * and other copyright owners as documented in JGit's IP log.
- *
- * This program and the accompanying materials are made available
- * under the terms of the Eclipse Distribution License v1.0 which
- * accompanies this distribution, is reproduced below, and is
- * available at http://www.eclipse.org/org/documents/edl-v10.php
- *
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or
- * without modification, are permitted provided that the following
- * conditions are met:
- *
- * - Redistributions of source code must retain the above copyright
- *   notice, this list of conditions and the following disclaimer.
- *
- * - Redistributions in binary form must reproduce the above
- *   copyright notice, this list of conditions and the following
- *   disclaimer in the documentation and/or other materials provided
- *   with the distribution.
- *
- * - Neither the name of the Eclipse Foundation, Inc. nor the
- *   names of its contributors may be used to endorse or promote
- *   products derived from this software without specific prior
- *   written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
- * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
- * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
- * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-#include "xinclude.h"
-#include "xtypes.h"
-#include "xdiff.h"
-
-#define MAX_PTR	UINT_MAX
-#define MAX_CNT	UINT_MAX
-
-#define LINE_END(n) (line##n + count##n - 1)
-#define LINE_END_PTR(n) (*line##n + *count##n - 1)
-
-struct histindex {
-	struct record {
-		unsigned int ptr, cnt;
-		struct record *next;
-	} **records, /* an occurrence */
-	  **line_map; /* map of line to record chain */
-	chastore_t rcha;
-	unsigned int *next_ptrs;
-	unsigned int table_bits,
-		     records_size,
-		     line_map_size;
-
-	unsigned int max_chain_length,
-		     key_shift,
-		     ptr_shift;
-
-	unsigned int cnt,
-		     has_common;
-
-	xdfenv_t *env;
-	xpparam_t const *xpp;
-};
-
-struct region {
-	unsigned int begin1, end1;
-	unsigned int begin2, end2;
-};
-
-#define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])
-
-#define NEXT_PTR(index, ptr) \
-	(index->next_ptrs[(ptr) - index->ptr_shift])
-
-#define CNT(index, ptr) \
-	((LINE_MAP(index, ptr))->cnt)
-
-#define REC(env, s, l) \
-	(env->xdf##s.recs[l - 1])
-
-static int cmp_recs(xpparam_t const *xpp,
-	xrecord_t *r1, xrecord_t *r2)
-{
-	return r1->ha == r2->ha &&
-		xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
-			    xpp->flags);
-}
-
-#define CMP_ENV(xpp, env, s1, l1, s2, l2) \
-	(cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
-
-#define CMP(i, s1, l1, s2, l2) \
-	(cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
-
-#define TABLE_HASH(index, side, line) \
-	XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
-
-static int scanA(struct histindex *index, int line1, int count1)
-{
-	unsigned int ptr, tbl_idx;
-	unsigned int chain_len;
-	struct record **rec_chain, *rec;
-
-	for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
-		tbl_idx = TABLE_HASH(index, 1, ptr);
-		rec_chain = index->records + tbl_idx;
-		rec = *rec_chain;
-
-		chain_len = 0;
-		while (rec) {
-			if (CMP(index, 1, rec->ptr, 1, ptr)) {
-				/*
-				 * ptr is identical to another element. Insert
-				 * it onto the front of the existing element
-				 * chain.
-				 */
-				NEXT_PTR(index, ptr) = rec->ptr;
-				rec->ptr = ptr;
-				/* cap rec->cnt at MAX_CNT */
-				rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
-				LINE_MAP(index, ptr) = rec;
-				goto continue_scan;
-			}
-
-			rec = rec->next;
-			chain_len++;
-		}
-
-		if (chain_len == index->max_chain_length)
-			return -1;
-
-		/*
-		 * This is the first time we have ever seen this particular
-		 * element in the sequence. Construct a new chain for it.
-		 */
-		if (!(rec = xdl_cha_alloc(&index->rcha)))
-			return -1;
-		rec->ptr = ptr;
-		rec->cnt = 1;
-		rec->next = *rec_chain;
-		*rec_chain = rec;
-		LINE_MAP(index, ptr) = rec;
-
-continue_scan:
-		; /* no op */
-	}
-
-	return 0;
-}
-
-static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
-	int line1, int count1, int line2, int count2)
-{
-	unsigned int b_next = b_ptr + 1;
-	struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
-	unsigned int as, ae, bs, be, np, rc;
-	int should_break;
-
-	for (; rec; rec = rec->next) {
-		if (rec->cnt > index->cnt) {
-			if (!index->has_common)
-				index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
-			continue;
-		}
-
-		as = rec->ptr;
-		if (!CMP(index, 1, as, 2, b_ptr))
-			continue;
-
-		index->has_common = 1;
-		for (;;) {
-			should_break = 0;
-			np = NEXT_PTR(index, as);
-			bs = b_ptr;
-			ae = as;
-			be = bs;
-			rc = rec->cnt;
-
-			while (line1 < as && line2 < bs
-				&& CMP(index, 1, as - 1, 2, bs - 1)) {
-				as--;
-				bs--;
-				if (1 < rc)
-					rc = XDL_MIN(rc, CNT(index, as));
-			}
-			while (ae < LINE_END(1) && be < LINE_END(2)
-				&& CMP(index, 1, ae + 1, 2, be + 1)) {
-				ae++;
-				be++;
-				if (1 < rc)
-					rc = XDL_MIN(rc, CNT(index, ae));
-			}
-
-			if (b_next <= be)
-				b_next = be + 1;
-			if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
-				lcs->begin1 = as;
-				lcs->begin2 = bs;
-				lcs->end1 = ae;
-				lcs->end2 = be;
-				index->cnt = rc;
-			}
-
-			if (np == 0)
-				break;
-
-			while (np <= ae) {
-				np = NEXT_PTR(index, np);
-				if (np == 0) {
-					should_break = 1;
-					break;
-				}
-			}
-
-			if (should_break)
-				break;
-
-			as = np;
-		}
-	}
-	return b_next;
-}
-
-static int find_lcs(struct histindex *index, struct region *lcs,
-	int line1, int count1, int line2, int count2) {
-	int b_ptr;
-
-	if (scanA(index, line1, count1))
-		return -1;
-
-	index->cnt = index->max_chain_length + 1;
-
-	for (b_ptr = line2; b_ptr <= LINE_END(2); )
-		b_ptr = try_lcs(index, lcs, b_ptr, line1, count1, line2, count2);
-
-	return index->has_common && index->max_chain_length < index->cnt;
-}
-
-static int fall_back_to_classic_diff(struct histindex *index,
-		int line1, int count1, int line2, int count2)
-{
-	xpparam_t xpp;
-	xpp.flags = index->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
-
-	return xdl_fall_back_diff(index->env, &xpp,
-				  line1, count1, line2, count2);
-}
-
-static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
-	int line1, int count1, int line2, int count2)
-{
-	struct histindex index;
-	struct region lcs;
-	int sz;
-	int result = -1;
-
-	if (count1 <= 0 && count2 <= 0)
-		return 0;
-
-	if (LINE_END(1) >= MAX_PTR)
-		return -1;
-
-	if (!count1) {
-		while(count2--)
-			env->xdf2.rchg[line2++ - 1] = 1;
-		return 0;
-	} else if (!count2) {
-		while(count1--)
-			env->xdf1.rchg[line1++ - 1] = 1;
-		return 0;
-	}
-
-	memset(&index, 0, sizeof(index));
-
-	index.env = env;
-	index.xpp = xpp;
-
-	index.records = NULL;
-	index.line_map = NULL;
-	/* in case of early xdl_cha_free() */
-	index.rcha.head = NULL;
-
-	index.table_bits = xdl_hashbits(count1);
-	sz = index.records_size = 1 << index.table_bits;
-	sz *= sizeof(struct record *);
-	if (!(index.records = (struct record **) xdl_malloc(sz)))
-		goto cleanup;
-	memset(index.records, 0, sz);
-
-	sz = index.line_map_size = count1;
-	sz *= sizeof(struct record *);
-	if (!(index.line_map = (struct record **) xdl_malloc(sz)))
-		goto cleanup;
-	memset(index.line_map, 0, sz);
-
-	sz = index.line_map_size;
-	sz *= sizeof(unsigned int);
-	if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
-		goto cleanup;
-	memset(index.next_ptrs, 0, sz);
-
-	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
-	if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
-		goto cleanup;
-
-	index.ptr_shift = line1;
-	index.max_chain_length = 64;
-
-	memset(&lcs, 0, sizeof(lcs));
-	if (find_lcs(&index, &lcs, line1, count1, line2, count2))
-		result = fall_back_to_classic_diff(&index, line1, count1, line2, count2);
-	else {
-		if (lcs.begin1 == 0 && lcs.begin2 == 0) {
-			while (count1--)
-				env->xdf1.rchg[line1++ - 1] = 1;
-			while (count2--)
-				env->xdf2.rchg[line2++ - 1] = 1;
-			result = 0;
-		} else {
-			result = histogram_diff(xpp, env,
-						line1, lcs.begin1 - line1,
-						line2, lcs.begin2 - line2);
-			if (result)
-				goto cleanup;
-			result = histogram_diff(xpp, env,
-						lcs.end1 + 1, LINE_END(1) - lcs.end1,
-						lcs.end2 + 1, LINE_END(2) - lcs.end2);
-			if (result)
-				goto cleanup;
-		}
-	}
-
-cleanup:
-	xdl_free(index.records);
-	xdl_free(index.line_map);
-	xdl_free(index.next_ptrs);
-	xdl_cha_free(&index.rcha);
-
-	return result;
-}
-
-int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
-	xpparam_t const *xpp, xdfenv_t *env)
-{
-	if (xdl_prepare_env(file1, file2, xpp, env) < 0)
-		return -1;
-
-	return histogram_diff(xpp, env,
-		env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
-		env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
-}

--- a/mercurial/thirdparty/xdiff/xpatience.c	Sat Mar 03 10:39:43 2018 -0800
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,390 +0,0 @@
-/*
- *  LibXDiff by Davide Libenzi ( File Differential Library )
- *  Copyright (C) 2003-2016 Davide Libenzi, Johannes E. Schindelin
- *
- *  This library is free software; you can redistribute it and/or
- *  modify it under the terms of the GNU Lesser General Public
- *  License as published by the Free Software Foundation; either
- *  version 2.1 of the License, or (at your option) any later version.
- *
- *  This library is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
- *  Lesser General Public License for more details.
- *
- *  You should have received a copy of the GNU Lesser General Public
- *  License along with this library; if not, see
- *  <http://www.gnu.org/licenses/>.
- *
- *  Davide Libenzi <davidel@xmailserver.org>
- *
- */
-#include "xinclude.h"
-#include "xtypes.h"
-#include "xdiff.h"
-
-/*
- * The basic idea of patience diff is to find lines that are unique in
- * both files.  These are intuitively the ones that we want to see as
- * common lines.
- *
- * The maximal ordered sequence of such line pairs (where ordered means
- * that the order in the sequence agrees with the order of the lines in
- * both files) naturally defines an initial set of common lines.
- *
- * Now, the algorithm tries to extend the set of common lines by growing
- * the line ranges where the files have identical lines.
- *
- * Between those common lines, the patience diff algorithm is applied
- * recursively, until no unique line pairs can be found; these line ranges
- * are handled by the well-known Myers algorithm.
- */
-
-#define NON_UNIQUE ULONG_MAX
-
-/*
- * This is a hash mapping from line hash to line numbers in the first and
- * second file.
- */
-struct hashmap {
-	int nr, alloc;
-	struct entry {
-		unsigned long hash;
-		/*
-		 * 0 = unused entry, 1 = first line, 2 = second, etc.
-		 * line2 is NON_UNIQUE if the line is not unique
-		 * in either the first or the second file.
-		 */
-		unsigned long line1, line2;
-		/*
-		 * "next" & "previous" are used for the longest common
-		 * sequence;
-		 * initially, "next" reflects only the order in file1.
-		 */
-		struct entry *next, *previous;
-
-		/*
-		 * If 1, this entry can serve as an anchor. See
-		 * Documentation/diff-options.txt for more information.
-		 */
-		unsigned anchor : 1;
-	} *entries, *first, *last;
-	/* were common records found? */
-	unsigned long has_matches;
-	mmfile_t *file1, *file2;
-	xdfenv_t *env;
-	xpparam_t const *xpp;
-};
-
-static int is_anchor(xpparam_t const *xpp, const char *line)
-{
-	int i;
-	for (i = 0; i < xpp->anchors_nr; i++) {
-		if (!strncmp(line, xpp->anchors[i], strlen(xpp->anchors[i])))
-			return 1;
-	}
-	return 0;
-}
-
-/* The argument "pass" is 1 for the first file, 2 for the second. */
-static void insert_record(xpparam_t const *xpp, int line, struct hashmap *map,
-			  int pass)
-{
-	xrecord_t **records = pass == 1 ?
-		map->env->xdf1.recs : map->env->xdf2.recs;
-	xrecord_t *record = records[line - 1], *other;
-	/*
-	 * After xdl_prepare_env() (or more precisely, due to
-	 * xdl_classify_record()), the "ha" member of the records (AKA lines)
-	 * is _not_ the hash anymore, but a linearized version of it.  In
-	 * other words, the "ha" member is guaranteed to start with 0 and
-	 * the second record's ha can only be 0 or 1, etc.
-	 *
-	 * So we multiply ha by 2 in the hope that the hashing was
-	 * "unique enough".
-	 */
-	int index = (int)((record->ha << 1) % map->alloc);
-
-	while (map->entries[index].line1) {
-		other = map->env->xdf1.recs[map->entries[index].line1 - 1];
-		if (map->entries[index].hash != record->ha ||
-				!xdl_recmatch(record->ptr, record->size,
-					other->ptr, other->size,
-					map->xpp->flags)) {
-			if (++index >= map->alloc)
-				index = 0;
-			continue;
-		}
-		if (pass == 2)
-			map->has_matches = 1;
-		if (pass == 1 || map->entries[index].line2)
-			map->entries[index].line2 = NON_UNIQUE;
-		else
-			map->entries[index].line2 = line;
-		return;
-	}
-	if (pass == 2)
-		return;
-	map->entries[index].line1 = line;
-	map->entries[index].hash = record->ha;
-	map->entries[index].anchor = is_anchor(xpp, map->env->xdf1.recs[line - 1]->ptr);
-	if (!map->first)
-		map->first = map->entries + index;
-	if (map->last) {
-		map->last->next = map->entries + index;
-		map->entries[index].previous = map->last;
-	}
-	map->last = map->entries + index;
-	map->nr++;
-}
-
-/*
- * This function has to be called for each recursion into the inter-hunk
- * parts, as previously non-unique lines can become unique when being
- * restricted to a smaller part of the files.
- *
- * It is assumed that env has been prepared using xdl_prepare().
- */
-static int fill_hashmap(mmfile_t *file1, mmfile_t *file2,
-		xpparam_t const *xpp, xdfenv_t *env,
-		struct hashmap *result,
-		int line1, int count1, int line2, int count2)
-{
-	result->file1 = file1;
-	result->file2 = file2;
-	result->xpp = xpp;
-	result->env = env;
-
-	/* We know exactly how large we want the hash map */
-	result->alloc = count1 * 2;
-	result->entries = (struct entry *)
-		xdl_malloc(result->alloc * sizeof(struct entry));
-	if (!result->entries)
-		return -1;
-	memset(result->entries, 0, result->alloc * sizeof(struct entry));
-
-	/* First, fill with entries from the first file */
-	while (count1--)
-		insert_record(xpp, line1++, result, 1);
-
-	/* Then search for matches in the second file */
-	while (count2--)
-		insert_record(xpp, line2++, result, 2);
-
-	return 0;
-}
-
-/*
- * Find the longest sequence with a smaller last element (meaning a smaller
- * line2, as we construct the sequence with entries ordered by line1).
- */
-static int binary_search(struct entry **sequence, int longest,
-		struct entry *entry)
-{
-	int left = -1, right = longest;
-
-	while (left + 1 < right) {
-		int middle = left + (right - left) / 2;
-		/* by construction, no two entries can be equal */
-		if (sequence[middle]->line2 > entry->line2)
-			right = middle;
-		else
-			left = middle;
-	}
-	/* return the index in "sequence", _not_ the sequence length */
-	return left;
-}
-
-/*
- * The idea is to start with the list of common unique lines sorted by
- * the order in file1.  For each of these pairs, the longest (partial)
- * sequence whose last element's line2 is smaller is determined.
- *
- * For efficiency, the sequences are kept in a list containing exactly one
- * item per sequence length: the sequence with the smallest last
- * element (in terms of line2).
- */
-static struct entry *find_longest_common_sequence(struct hashmap *map)
-{
-	struct entry **sequence = xdl_malloc(map->nr * sizeof(struct entry *));
-	int longest = 0, i;
-	struct entry *entry;
-
-	/*
-	 * If not -1, this entry in sequence must never be overridden.
-	 * Therefore, overriding entries before this has no effect, so
-	 * do not do that either.
-	 */
-	int anchor_i = -1;
-
-	for (entry = map->first; entry; entry = entry->next) {
-		if (!entry->line2 || entry->line2 == NON_UNIQUE)
-			continue;
-		i = binary_search(sequence, longest, entry);
-		entry->previous = i < 0 ? NULL : sequence[i];
-		++i;
-		if (i <= anchor_i)
-			continue;
-		sequence[i] = entry;
-		if (entry->anchor) {
-			anchor_i = i;
-			longest = anchor_i + 1;
-		} else if (i == longest) {
-			longest++;
-		}
-	}
-
-	/* No common unique lines were found */
-	if (!longest) {
-		xdl_free(sequence);
-		return NULL;
-	}
-
-	/* Iterate starting at the last element, adjusting the "next" members */
-	entry = sequence[longest - 1];
-	entry->next = NULL;
-	while (entry->previous) {
-		entry->previous->next = entry;
-		entry = entry->previous;
-	}
-	xdl_free(sequence);
-	return entry;
-}
-
-static int match(struct hashmap *map, int line1, int line2)
-{
-	xrecord_t *record1 = map->env->xdf1.recs[line1 - 1];
-	xrecord_t *record2 = map->env->xdf2.recs[line2 - 1];
-	return xdl_recmatch(record1->ptr, record1->size,
-		record2->ptr, record2->size, map->xpp->flags);
-}
-
-static int patience_diff(mmfile_t *file1, mmfile_t *file2,
-		xpparam_t const *xpp, xdfenv_t *env,
-		int line1, int count1, int line2, int count2);
-
-static int walk_common_sequence(struct hashmap *map, struct entry *first,
-		int line1, int count1, int line2, int count2)
-{
-	int end1 = line1 + count1, end2 = line2 + count2;
-	int next1, next2;
-
-	for (;;) {
-		/* Try to grow the line ranges of common lines */
-		if (first) {
-			next1 = first->line1;
-			next2 = first->line2;
-			while (next1 > line1 && next2 > line2 &&
-					match(map, next1 - 1, next2 - 1)) {
-				next1--;
-				next2--;
-			}
-		} else {
-			next1 = end1;
-			next2 = end2;
-		}
-		while (line1 < next1 && line2 < next2 &&
-				match(map, line1, line2)) {
-			line1++;
-			line2++;
-		}
-
-		/* Recurse */
-		if (next1 > line1 || next2 > line2) {
-			struct hashmap submap;
-
-			memset(&submap, 0, sizeof(submap));
-			if (patience_diff(map->file1, map->file2,
-					map->xpp, map->env,
-					line1, next1 - line1,
-					line2, next2 - line2))
-				return -1;
-		}
-
-		if (!first)
-			return 0;
-
-		while (first->next &&
-				first->next->line1 == first->line1 + 1 &&
-				first->next->line2 == first->line2 + 1)
-			first = first->next;
-
-		line1 = first->line1 + 1;
-		line2 = first->line2 + 1;
-
-		first = first->next;
-	}
-}
-
-static int fall_back_to_classic_diff(struct hashmap *map,
-		int line1, int count1, int line2, int count2)
-{
-	xpparam_t xpp;
-	xpp.flags = map->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
-
-	return xdl_fall_back_diff(map->env, &xpp,
-				  line1, count1, line2, count2);
-}
-
-/*
- * Recursively find the longest common sequence of unique lines,
- * and if none was found, ask xdl_do_diff() to do the job.
- *
- * This function assumes that env was prepared with xdl_prepare_env().
- */
-static int patience_diff(mmfile_t *file1, mmfile_t *file2,
-		xpparam_t const *xpp, xdfenv_t *env,
-		int line1, int count1, int line2, int count2)
-{
-	struct hashmap map;
-	struct entry *first;
-	int result = 0;
-
-	/* trivial case: one side is empty */
-	if (!count1) {
-		while(count2--)
-			env->xdf2.rchg[line2++ - 1] = 1;
-		return 0;
-	} else if (!count2) {
-		while(count1--)
-			env->xdf1.rchg[line1++ - 1] = 1;
-		return 0;
-	}
-
-	memset(&map, 0, sizeof(map));
-	if (fill_hashmap(file1, file2, xpp, env, &map,
-			line1, count1, line2, count2))
-		return -1;
-
-	/* are there any matching lines at all? */
-	if (!map.has_matches) {
-		while(count1--)
-			env->xdf1.rchg[line1++ - 1] = 1;
-		while(count2--)
-			env->xdf2.rchg[line2++ - 1] = 1;
-		xdl_free(map.entries);
-		return 0;
-	}
-
-	first = find_longest_common_sequence(&map);
-	if (first)
-		result = walk_common_sequence(&map, first,
-			line1, count1, line2, count2);
-	else
-		result = fall_back_to_classic_diff(&map,
-			line1, count1, line2, count2);
-
-	xdl_free(map.entries);
-	return result;
-}
-
-int xdl_do_patience_diff(mmfile_t *file1, mmfile_t *file2,
-		xpparam_t const *xpp, xdfenv_t *env)
-{
-	if (xdl_prepare_env(file1, file2, xpp, env) < 0)
-		return -1;
-
-	/* environment is cleaned up in xdl_diff() */
-	return patience_diff(file1, file2, xpp, env,
-			1, env->xdf1.nrec, 1, env->xdf2.nrec);
-}

--- a/mercurial/thirdparty/xdiff/xprepare.c	Sat Mar 03 10:39:43 2018 -0800
+++ b/mercurial/thirdparty/xdiff/xprepare.c	Sat Mar 03 10:39:55 2018 -0800
@@ -27,7 +27,6 @@
 #define XDL_MAX_EQLIMIT 1024
 #define XDL_SIMSCAN_WINDOW 100
 #define XDL_GUESS_NLINES1 256
-#define XDL_GUESS_NLINES2 20
 
 
 typedef struct s_xdlclass {
@@ -181,9 +180,7 @@
 	if (!(recs = (xrecord_t **) xdl_malloc(narec * sizeof(xrecord_t *))))
 		goto abort;
 
-	if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
-		hbits = hsize = 0;
-	else {
+	{
 		hbits = xdl_hashbits((unsigned int) narec);
 		hsize = 1 << hbits;
 		if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *))))
@@ -209,8 +206,7 @@
 			crec->ha = hav;
 			recs[nrec++] = crec;
 
-			if ((XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
-			    xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
+			if (xdl_classify_record(pass, cf, rhash, hbits, crec) < 0)
 				goto abort;
 		}
 	}
@@ -266,21 +262,12 @@
 
 	memset(&cf, 0, sizeof(cf));
 
-	/*
-	 * For histogram diff, we can afford a smaller sample size and
-	 * thus a poorer estimate of the number of lines, as the hash
-	 * table (rhash) won't be filled up/grown. The number of lines
-	 * (nrecs) will be updated correctly anyway by
-	 * xdl_prepare_ctx().
-	 */
-	sample = (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF
-		  ? XDL_GUESS_NLINES2 : XDL_GUESS_NLINES1);
+	sample = XDL_GUESS_NLINES1;
 
 	enl1 = xdl_guess_lines(mf1, sample) + 1;
 	enl2 = xdl_guess_lines(mf2, sample) + 1;
 
-	if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF &&
-	    xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
+	if (xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0)
 		return -1;
 
 	if (xdl_prepare_ctx(1, mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
@@ -295,18 +282,14 @@
 		return -1;
 	}
 
-	if ((XDF_DIFF_ALG(xpp->flags) != XDF_PATIENCE_DIFF) &&
-	    (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF) &&
-	    xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {
-
+	if (xdl_optimize_ctxs(&cf, &xe->xdf1, &xe->xdf2) < 0) {
 		xdl_free_ctx(&xe->xdf2);
 		xdl_free_ctx(&xe->xdf1);
 		xdl_free_classifier(&cf);
 		return -1;
 	}
 
-	if (XDF_DIFF_ALG(xpp->flags) != XDF_HISTOGRAM_DIFF)
-		xdl_free_classifier(&cf);
+	xdl_free_classifier(&cf);
 
 	return 0;
 }