Use java-diff-utils for diffing in partest.

We now use the unified diff format, hence the updated check files.

It's not clear to me how partest's classpath is managed,
but the approach in this commit works for the ant task and script invocation.
The diffutils jar is injected in the parent classloader.

6 files changed, 26 insertions, 1503 deletions

diff --git a/src/partest/scala/tools/partest/nest/Diff.java b/src/partest/scala/tools/partest/nest/Diff.java
deleted file mode 100644
index f69fc6858b..0000000000
--- a/src/partest/scala/tools/partest/nest/Diff.java
+++ /dev/null
@@ -1,873 +0,0 @@
-
-package scala.tools.partest.nest;
-
-import java.util.Hashtable;
-
-/** A class to compare IndexedSeqs of objects.  The result of comparison
-    is a list of <code>change</code> objects which form an
-    edit script.  The objects compared are traditionally lines
-    of text from two files.  Comparison options such as "ignore
-    whitespace" are implemented by modifying the <code>equals</code>
-    and <code>hashcode</code> methods for the objects compared.
-<p>
-   The basic algorithm is described in: </br>
-   "An O(ND) Difference Algorithm and its Variations", Eugene Myers,
-   Algorithmica Vol. 1 No. 2, 1986, p 251.
-<p>
-   This class outputs different results from GNU diff 1.15 on some
-   inputs.  Our results are actually better (smaller change list, smaller
-   total size of changes), but it would be nice to know why.  Perhaps
-   there is a memory overwrite bug in GNU diff 1.15.
-
-  @author Stuart D. Gathman, translated from GNU diff 1.15
-    Copyright (C) 2000  Business Management Systems, Inc.
-<p>
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation; either version 1, or (at your option)
-    any later version.
-<p>
-    This program 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 General Public License for more details.
-<p>
-    You should have received a copy of the <a href=COPYING.txt>
-    GNU General Public License</a>
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
-
- */
-
-public class Diff {
-
-  /** Prepare to find differences between two arrays.  Each element of
-      the arrays is translated to an "equivalence number" based on
-      the result of <code>equals</code>.  The original Object arrays
-      are no longer needed for computing the differences.  They will
-      be needed again later to print the results of the comparison as
-      an edit script, if desired.
-   */
-  public Diff(Object[] a,Object[] b) {
-    Hashtable<Object, Integer> h = new Hashtable<Object, Integer>(a.length + b.length);
-    filevec[0] = new file_data(a,h);
-    filevec[1] = new file_data(b,h);
-  }
-
-  /** 1 more than the maximum equivalence value used for this or its
-     sibling file. */
-  private int equiv_max = 1;
-
-  /** When set to true, the comparison uses a heuristic to speed it up.
-    With this heuristic, for files with a constant small density
-    of changes, the algorithm is linear in the file size.  */
-  public boolean heuristic = false;
-
-  /** When set to true, the algorithm returns a guarranteed minimal
-      set of changes.  This makes things slower, sometimes much slower. */
-  public boolean no_discards = false;
-
-  private int[] xvec, yvec;	/* IndexedSeqs being compared. */
-  private int[] fdiag;		/* IndexedSeq, indexed by diagonal, containing
-				   the X coordinate of the point furthest
-				   along the given diagonal in the forward
-				   search of the edit matrix. */
-  private int[] bdiag;		/* IndexedSeq, indexed by diagonal, containing
-				   the X coordinate of the point furthest
-				   along the given diagonal in the backward
-				   search of the edit matrix. */
-  private int fdiagoff, bdiagoff;
-  private final file_data[] filevec = new file_data[2];
-  private int cost;
-
-  /** Find the midpoint of the shortest edit script for a specified
-     portion of the two files.
-
-     We scan from the beginnings of the files, and simultaneously from the ends,
-     doing a breadth-first search through the space of edit-sequence.
-     When the two searches meet, we have found the midpoint of the shortest
-     edit sequence.
-
-     The value returned is the number of the diagonal on which the midpoint lies.
-     The diagonal number equals the number of inserted lines minus the number
-     of deleted lines (counting only lines before the midpoint).
-     The edit cost is stored into COST; this is the total number of
-     lines inserted or deleted (counting only lines before the midpoint).
-
-     This function assumes that the first lines of the specified portions
-     of the two files do not match, and likewise that the last lines do not
-     match.  The caller must trim matching lines from the beginning and end
-     of the portions it is going to specify.
-
-     Note that if we return the "wrong" diagonal value, or if
-     the value of bdiag at that diagonal is "wrong",
-     the worst this can do is cause suboptimal diff output.
-     It cannot cause incorrect diff output.  */
-
-  private int diag (int xoff, int xlim, int yoff, int ylim) {
-    final int[] fd = fdiag;	// Give the compiler a chance.
-    final int[] bd = bdiag;	// Additional help for the compiler.
-    final int[] xv = xvec;		// Still more help for the compiler.
-    final int[] yv = yvec;		// And more and more . . .
-    final int dmin = xoff - ylim;	// Minimum valid diagonal.
-    final int dmax = xlim - yoff;	// Maximum valid diagonal.
-    final int fmid = xoff - yoff;	// Center diagonal of top-down search.
-    final int bmid = xlim - ylim;	// Center diagonal of bottom-up search.
-    int fmin = fmid, fmax = fmid;	// Limits of top-down search.
-    int bmin = bmid, bmax = bmid;	// Limits of bottom-up search.
-    /* True if southeast corner is on an odd
-				     diagonal with respect to the northwest. */
-    final boolean odd = (fmid - bmid & 1) != 0;
-
-    fd[fdiagoff + fmid] = xoff;
-    bd[bdiagoff + bmid] = xlim;
-
-    for (int c = 1;; ++c)
-      {
-	int d;			/* Active diagonal. */
-	boolean big_snake = false;
-
-	/* Extend the top-down search by an edit step in each diagonal. */
-	if (fmin > dmin)
-	  fd[fdiagoff + --fmin - 1] = -1;
-	else
-	  ++fmin;
-	if (fmax < dmax)
-	  fd[fdiagoff + ++fmax + 1] = -1;
-	else
-	  --fmax;
-	for (d = fmax; d >= fmin; d -= 2)
-	  {
-	    int x, y, oldx, tlo = fd[fdiagoff + d - 1], thi = fd[fdiagoff + d + 1];
-
-	    if (tlo >= thi)
-	      x = tlo + 1;
-	    else
-	      x = thi;
-	    oldx = x;
-	    y = x - d;
-	    while (x < xlim && y < ylim && xv[x] == yv[y]) {
-	      ++x; ++y;
-	    }
-	    if (x - oldx > 20)
-	      big_snake = true;
-	    fd[fdiagoff + d] = x;
-	    if (odd && bmin <= d && d <= bmax && bd[bdiagoff + d] <= fd[fdiagoff + d])
-	      {
-		cost = 2 * c - 1;
-		return d;
-	      }
-	  }
-
-	/* Similar extend the bottom-up search. */
-	if (bmin > dmin)
-	  bd[bdiagoff + --bmin - 1] = Integer.MAX_VALUE;
-	else
-	  ++bmin;
-	if (bmax < dmax)
-	  bd[bdiagoff + ++bmax + 1] = Integer.MAX_VALUE;
-	else
-	  --bmax;
-	for (d = bmax; d >= bmin; d -= 2)
-	  {
-	    int x, y, oldx, tlo = bd[bdiagoff + d - 1], thi = bd[bdiagoff + d + 1];
-
-	    if (tlo < thi)
-	      x = tlo;
-	    else
-	      x = thi - 1;
-	    oldx = x;
-	    y = x - d;
-	    while (x > xoff && y > yoff && xv[x - 1] == yv[y - 1]) {
-	      --x; --y;
-	    }
-	    if (oldx - x > 20)
-	      big_snake = true;
-	    bd[bdiagoff + d] = x;
-	    if (!odd && fmin <= d && d <= fmax && bd[bdiagoff + d] <= fd[fdiagoff + d])
-	      {
-		cost = 2 * c;
-		return d;
-	      }
-	  }
-
-	/* Heuristic: check occasionally for a diagonal that has made
-	   lots of progress compared with the edit distance.
-	   If we have any such, find the one that has made the most
-	   progress and return it as if it had succeeded.
-
-	   With this heuristic, for files with a constant small density
-	   of changes, the algorithm is linear in the file size.  */
-
-	if (c > 200 && big_snake && heuristic)
-	  {
-	    int best = 0;
-	    int bestpos = -1;
-
-	    for (d = fmax; d >= fmin; d -= 2)
-	      {
-		int dd = d - fmid;
-		if ((fd[fdiagoff + d] - xoff)*2 - dd > 12 * (c + (dd > 0 ? dd : -dd)))
-		  {
-		    if (fd[fdiagoff + d] * 2 - dd > best
-			&& fd[fdiagoff + d] - xoff > 20
-			&& fd[fdiagoff + d] - d - yoff > 20)
-		      {
-			int k;
-			int x = fd[fdiagoff + d];
-
-			/* We have a good enough best diagonal;
-			   now insist that it end with a significant snake.  */
-			for (k = 1; k <= 20; k++)
-			  if (xvec[x - k] != yvec[x - d - k])
-			    break;
-
-			if (k == 21)
-			  {
-			    best = fd[fdiagoff + d] * 2 - dd;
-			    bestpos = d;
-			  }
-		      }
-		  }
-	      }
-	    if (best > 0)
-	      {
-		cost = 2 * c - 1;
-		return bestpos;
-	      }
-
-	    best = 0;
-	    for (d = bmax; d >= bmin; d -= 2)
-	      {
-		int dd = d - bmid;
-		if ((xlim - bd[bdiagoff + d])*2 + dd > 12 * (c + (dd > 0 ? dd : -dd)))
-		  {
-		    if ((xlim - bd[bdiagoff + d]) * 2 + dd > best
-			&& xlim - bd[bdiagoff + d] > 20
-			&& ylim - (bd[bdiagoff + d] - d) > 20)
-		      {
-			/* We have a good enough best diagonal;
-			   now insist that it end with a significant snake.  */
-			int k;
-			int x = bd[bdiagoff + d];
-
-			for (k = 0; k < 20; k++)
-			  if (xvec[x + k] != yvec[x - d + k])
-			    break;
-			if (k == 20)
-			  {
-			    best = (xlim - bd[bdiagoff + d]) * 2 + dd;
-			    bestpos = d;
-			  }
-		      }
-		  }
-	      }
-	    if (best > 0)
-	      {
-		cost = 2 * c - 1;
-		return bestpos;
-	      }
-	  }
-      }
-  }
-
-  /** Compare in detail contiguous subsequences of the two files
-     which are known, as a whole, to match each other.
-
-     The results are recorded in the IndexedSeqs filevec[N].changed_flag, by
-     storing a 1 in the element for each line that is an insertion or deletion.
-
-     The subsequence of file 0 is [XOFF, XLIM) and likewise for file 1.
-
-     Note that XLIM, YLIM are exclusive bounds.
-     All line numbers are origin-0 and discarded lines are not counted.  */
-
-  private void compareseq (int xoff, int xlim, int yoff, int ylim) {
-    /* Slide down the bottom initial diagonal. */
-    while (xoff < xlim && yoff < ylim && xvec[xoff] == yvec[yoff]) {
-      ++xoff; ++yoff;
-    }
-    /* Slide up the top initial diagonal. */
-    while (xlim > xoff && ylim > yoff && xvec[xlim - 1] == yvec[ylim - 1]) {
-      --xlim; --ylim;
-    }
-
-    /* Handle simple cases. */
-    if (xoff == xlim)
-      while (yoff < ylim)
-	filevec[1].changed_flag[1+filevec[1].realindexes[yoff++]] = true;
-    else if (yoff == ylim)
-      while (xoff < xlim)
-	filevec[0].changed_flag[1+filevec[0].realindexes[xoff++]] = true;
-    else
-      {
-	/* Find a point of correspondence in the middle of the files.  */
-
-	int d = diag (xoff, xlim, yoff, ylim);
-	int c = cost;
-	int f = fdiag[fdiagoff + d];
-	int b = bdiag[bdiagoff + d];
-
-	if (c == 1)
-	  {
-	    /* This should be impossible, because it implies that
-	       one of the two subsequences is empty,
-	       and that case was handled above without calling `diag'.
-	       Let's verify that this is true.  */
-	    throw new IllegalArgumentException("Empty subsequence");
-	  }
-	else
-	  {
-	    /* Use that point to split this problem into two subproblems.  */
-	    compareseq (xoff, b, yoff, b - d);
-	    /* This used to use f instead of b,
-	       but that is incorrect!
-	       It is not necessarily the case that diagonal d
-	       has a snake from b to f.  */
-	    compareseq (b, xlim, b - d, ylim);
-	  }
-      }
-  }
-
-  /** Discard lines from one file that have no matches in the other file.
-   */
-
-  private void discard_confusing_lines() {
-    filevec[0].discard_confusing_lines(filevec[1]);
-    filevec[1].discard_confusing_lines(filevec[0]);
-  }
-
-  private boolean inhibit = false;
-
-  /** Adjust inserts/deletes of blank lines to join changes
-     as much as possible.
-   */
-
-  private void shift_boundaries() {
-    if (inhibit)
-      return;
-    filevec[0].shift_boundaries(filevec[1]);
-    filevec[1].shift_boundaries(filevec[0]);
-  }
-
-  public interface ScriptBuilder {
-  /** Scan the tables of which lines are inserted and deleted,
-     producing an edit script.
-   @param changed0 true for lines in first file which do not match 2nd
-   @param len0 number of lines in first file
-   @param changed1 true for lines in 2nd file which do not match 1st
-   @param len1 number of lines in 2nd file
-   @return a linked list of changes - or null
-   */
-    public change build_script(
-      boolean[] changed0,int len0,
-      boolean[] changed1,int len1
-    );
-  }
-
-  /** Scan the tables of which lines are inserted and deleted,
-     producing an edit script in reverse order.  */
-
-  static class ReverseScript implements ScriptBuilder {
-    public  change build_script(
-	final boolean[] changed0,int len0,
-	final boolean[] changed1,int len1)
-    {
-      change script = null;
-      int i0 = 0, i1 = 0;
-      while (i0 < len0 || i1 < len1) {
-	if (changed0[1+i0] || changed1[1+i1]) {
-	    int line0 = i0, line1 = i1;
-
-	    /* Find # lines changed here in each file.  */
-	    while (changed0[1+i0]) ++i0;
-	    while (changed1[1+i1]) ++i1;
-
-	    /* Record this change.  */
-	    script = new change(line0, line1, i0 - line0, i1 - line1, script);
-	}
-
-	/* We have reached lines in the two files that match each other.  */
-	i0++; i1++;
-      }
-
-      return script;
-    }
-  }
-
-  static class ForwardScript implements ScriptBuilder {
-    /** Scan the tables of which lines are inserted and deleted,
-       producing an edit script in forward order.  */
-    public change build_script(
-	  final boolean[] changed0,int len0,
-	  final boolean[] changed1,int len1)
-    {
-      change script = null;
-      int i0 = len0, i1 = len1;
-
-      while (i0 >= 0 || i1 >= 0)
-	{
-	  if (changed0[i0] || changed1[i1])
-	    {
-	      int line0 = i0, line1 = i1;
-
-	      /* Find # lines changed here in each file.  */
-	      while (changed0[i0]) --i0;
-	      while (changed1[i1]) --i1;
-
-	      /* Record this change.  */
-	      script = new change(i0, i1, line0 - i0, line1 - i1, script);
-	    }
-
-	  /* We have reached lines in the two files that match each other.  */
-	  i0--; i1--;
-	}
-
-      return script;
-    }
-  }
-
-  /** Standard ScriptBuilders. */
-  public final static ScriptBuilder
-    forwardScript = new ForwardScript(),
-    reverseScript = new ReverseScript();
-
-  /* Report the differences of two files.  DEPTH is the current directory
-     depth. */
-  public final change diff_2(final boolean reverse) {
-    return diff(reverse ? reverseScript : forwardScript);
-  }
-
-  /** Get the results of comparison as an edit script.  The script
-     is described by a list of changes.  The standard ScriptBuilder
-     implementations provide for forward and reverse edit scripts.
-     Alternate implementations could, for instance, list common elements
-     instead of differences.
-     @param bld	an object to build the script from change flags
-     @return the head of a list of changes
-   */
-  public change diff(final ScriptBuilder bld) {
-
-    /* Some lines are obviously insertions or deletions
-       because they don't match anything.  Detect them now,
-       and avoid even thinking about them in the main comparison algorithm.  */
-
-    discard_confusing_lines ();
-
-    /* Now do the main comparison algorithm, considering just the
-       undiscarded lines.  */
-
-    xvec = filevec[0].undiscarded;
-    yvec = filevec[1].undiscarded;
-
-    int diags =
-      filevec[0].nondiscarded_lines + filevec[1].nondiscarded_lines + 3;
-    fdiag = new int[diags];
-    fdiagoff = filevec[1].nondiscarded_lines + 1;
-    bdiag = new int[diags];
-    bdiagoff = filevec[1].nondiscarded_lines + 1;
-
-    compareseq (0, filevec[0].nondiscarded_lines,
-		0, filevec[1].nondiscarded_lines);
-    fdiag = null;
-    bdiag = null;
-
-    /* Modify the results slightly to make them prettier
-       in cases where that can validly be done.  */
-
-    shift_boundaries ();
-
-    /* Get the results of comparison in the form of a chain
-       of `struct change's -- an edit script.  */
-    return bld.build_script(
-      filevec[0].changed_flag,
-      filevec[0].buffered_lines,
-      filevec[1].changed_flag,
-      filevec[1].buffered_lines
-    );
-
-  }
-
-  /** The result of comparison is an "edit script": a chain of change objects.
-     Each change represents one place where some lines are deleted
-     and some are inserted.
-
-     LINE0 and LINE1 are the first affected lines in the two files (origin 0).
-     DELETED is the number of lines deleted here from file 0.
-     INSERTED is the number of lines inserted here in file 1.
-
-     If DELETED is 0 then LINE0 is the number of the line before
-     which the insertion was done; vice versa for INSERTED and LINE1.  */
-
-  public static class change {
-    /** Previous or next edit command. */
-    public change link;
-    /** # lines of file 1 changed here.  */
-    public final int inserted;
-    /** # lines of file 0 changed here.  */
-    public final int deleted;
-    /** Line number of 1st deleted line.  */
-    public final int line0;
-    /** Line number of 1st inserted line.  */
-    public final int line1;
-
-    /** Cons an additional entry onto the front of an edit script OLD.
-       LINE0 and LINE1 are the first affected lines in the two files (origin 0).
-       DELETED is the number of lines deleted here from file 0.
-       INSERTED is the number of lines inserted here in file 1.
-
-       If DELETED is 0 then LINE0 is the number of the line before
-       which the insertion was done; vice versa for INSERTED and LINE1.  */
-    public change(int line0, int line1, int deleted, int inserted, change old) {
-      this.line0 = line0;
-      this.line1 = line1;
-      this.inserted = inserted;
-      this.deleted = deleted;
-      this.link = old;
-      //System.err.println(line0+","+line1+","+inserted+","+deleted);
-    }
-  }
-
-  /** Data on one input file being compared.
-   */
-
-  class file_data {
-
-    /** Allocate changed array for the results of comparison.  */
-    void clear() {
-      /* Allocate a flag for each line of each file, saying whether that line
-	 is an insertion or deletion.
-	 Allocate an extra element, always zero, at each end of each IndexedSeq.
-       */
-      changed_flag = new boolean[buffered_lines + 2];
-    }
-
-    /** Return equiv_count[I] as the number of lines in this file
-       that fall in equivalence class I.
-         @return the array of equivalence class counts.
-     */
-    int[] equivCount() {
-      int[] equiv_count = new int[equiv_max];
-      for (int i = 0; i < buffered_lines; ++i)
-	++equiv_count[equivs[i]];
-      return equiv_count;
-    }
-
-    /** Discard lines that have no matches in another file.
-
-       A line which is discarded will not be considered by the actual
-       comparison algorithm; it will be as if that line were not in the file.
-       The file's `realindexes' table maps virtual line numbers
-       (which don't count the discarded lines) into real line numbers;
-       this is how the actual comparison algorithm produces results
-       that are comprehensible when the discarded lines are counted.
-<p>
-       When we discard a line, we also mark it as a deletion or insertion
-       so that it will be printed in the output.
-      @param f the other file
-     */
-    void discard_confusing_lines(file_data f) {
-      clear();
-    /* Set up table of which lines are going to be discarded. */
-      final byte[] discarded = discardable(f.equivCount());
-
-    /* Don't really discard the provisional lines except when they occur
-       in a run of discardables, with nonprovisionals at the beginning
-       and end.  */
-      filterDiscards(discarded);
-
-    /* Actually discard the lines. */
-      discard(discarded);
-    }
-
-    /** Mark to be discarded each line that matches no line of another file.
-       If a line matches many lines, mark it as provisionally discardable.
-       @see equivCount()
-       @param counts The count of each equivalence number for the other file.
-       @return 0=nondiscardable, 1=discardable or 2=provisionally discardable
-       	for each line
-     */
-
-    private byte[] discardable(final int[] counts) {
-      final int end = buffered_lines;
-      final byte[] discards = new byte[end];
-      final int[] equivs = this.equivs;
-      int many = 5;
-      int tem = end / 64;
-
-      /* Multiply MANY by approximate square root of number of lines.
-	 That is the threshold for provisionally discardable lines.  */
-      while ((tem = tem >> 2) > 0)
-	many *= 2;
-
-      for (int i = 0; i < end; i++)
-	{
-	  int nmatch;
-	  if (equivs[i] == 0)
-	    continue;
-	  nmatch = counts[equivs[i]];
-	  if (nmatch == 0)
-	    discards[i] = 1;
-	  else if (nmatch > many)
-	    discards[i] = 2;
-	}
-      return discards;
-    }
-
-    /** Don't really discard the provisional lines except when they occur
-       in a run of discardables, with nonprovisionals at the beginning
-       and end.  */
-
-    private void filterDiscards(final byte[] discards) {
-	final int end = buffered_lines;
-
-	for (int i = 0; i < end; i++)
-	  {
-	    /* Cancel provisional discards not in middle of run of discards.  */
-	    if (discards[i] == 2)
-	      discards[i] = 0;
-	    else if (discards[i] != 0)
-	      {
-		/* We have found a nonprovisional discard.  */
-		int j;
-		int length;
-		int provisional = 0;
-
-		/* Find end of this run of discardable lines.
-		   Count how many are provisionally discardable.  */
-		for (j = i; j < end; j++)
-		  {
-		    if (discards[j] == 0)
-		      break;
-		    if (discards[j] == 2)
-		      ++provisional;
-		  }
-
-		/* Cancel provisional discards at end, and shrink the run.  */
-		while (j > i && discards[j - 1] == 2) {
-		  discards[--j] = 0; --provisional;
-		}
-
-		/* Now we have the length of a run of discardable lines
-		   whose first and last are not provisional.  */
-		length = j - i;
-
-		/* If 1/4 of the lines in the run are provisional,
-		   cancel discarding of all provisional lines in the run.  */
-		if (provisional * 4 > length)
-		  {
-		    while (j > i)
-		      if (discards[--j] == 2)
-			discards[j] = 0;
-		  }
-		else
-		  {
-		    int consec;
-		    int minimum = 1;
-		    int tem = length / 4;
-
-		    /* MINIMUM is approximate square root of LENGTH/4.
-		       A subrun of two or more provisionals can stand
-		       when LENGTH is at least 16.
-		       A subrun of 4 or more can stand when LENGTH >= 64.  */
-		    while ((tem = tem >> 2) > 0)
-		      minimum *= 2;
-		    minimum++;
-
-		    /* Cancel any subrun of MINIMUM or more provisionals
-		       within the larger run.  */
-		    for (j = 0, consec = 0; j < length; j++)
-		      if (discards[i + j] != 2)
-			consec = 0;
-		      else if (minimum == ++consec)
-			/* Back up to start of subrun, to cancel it all.  */
-			j -= consec;
-		      else if (minimum < consec)
-			discards[i + j] = 0;
-
-		    /* Scan from beginning of run
-		       until we find 3 or more nonprovisionals in a row
-		       or until the first nonprovisional at least 8 lines in.
-		       Until that point, cancel any provisionals.  */
-		    for (j = 0, consec = 0; j < length; j++)
-		      {
-			if (j >= 8 && discards[i + j] == 1)
-			  break;
-			if (discards[i + j] == 2) {
-			  consec = 0; discards[i + j] = 0;
-			}
-			else if (discards[i + j] == 0)
-			  consec = 0;
-			else
-			  consec++;
-			if (consec == 3)
-			  break;
-		      }
-
-		    /* I advances to the last line of the run.  */
-		    i += length - 1;
-
-		    /* Same thing, from end.  */
-		    for (j = 0, consec = 0; j < length; j++)
-		      {
-			if (j >= 8 && discards[i - j] == 1)
-			  break;
-			if (discards[i - j] == 2) {
-			  consec = 0; discards[i - j] = 0;
-			}
-			else if (discards[i - j] == 0)
-			  consec = 0;
-			else
-			  consec++;
-			if (consec == 3)
-			  break;
-		      }
-		  }
-	      }
-	  }
-      }
-
-    /** Actually discard the lines.
-      @param discards flags lines to be discarded
-     */
-    private void discard(final byte[] discards) {
-      final int end = buffered_lines;
-      int j = 0;
-      for (int i = 0; i < end; ++i)
-	if (no_discards || discards[i] == 0)
-	  {
-	    undiscarded[j] = equivs[i];
-	    realindexes[j++] = i;
-	  }
-	else
-	  changed_flag[1+i] = true;
-      nondiscarded_lines = j;
-    }
-
-    file_data(Object[] data, Hashtable<Object, Integer> h) {
-      buffered_lines = data.length;
-
-      equivs = new int[buffered_lines];
-      undiscarded = new int[buffered_lines];
-      realindexes = new int[buffered_lines];
-
-      for (int i = 0; i < data.length; ++i) {
-        Integer ir = h.get(data[i]);
-	if (ir == null)
-	  h.put(data[i], new Integer(equivs[i] = equiv_max++));
-	else
-	  equivs[i] = ir.intValue();
-      }
-    }
-
-    /** Adjust inserts/deletes of blank lines to join changes
-       as much as possible.
-
-       We do something when a run of changed lines include a blank
-       line at one end and have an excluded blank line at the other.
-       We are free to choose which blank line is included.
-       `compareseq' always chooses the one at the beginning,
-       but usually it is cleaner to consider the following blank line
-       to be the "change".  The only exception is if the preceding blank line
-       would join this change to other changes.
-      @param f the file being compared against
-    */
-
-    void shift_boundaries(file_data f) {
-      final boolean[] changed = changed_flag;
-      final boolean[] other_changed = f.changed_flag;
-      int i = 0;
-      int j = 0;
-      int i_end = buffered_lines;
-      int preceding = -1;
-      int other_preceding = -1;
-
-      for (;;)
-	{
-	  int start, end, other_start;
-
-	  /* Scan forwards to find beginning of another run of changes.
-	     Also keep track of the corresponding point in the other file.  */
-
-	  while (i < i_end && !changed[1+i])
-	    {
-	      while (other_changed[1+j++])
-		/* Non-corresponding lines in the other file
-		   will count as the preceding batch of changes.  */
-		other_preceding = j;
-	      i++;
-	    }
-
-	  if (i == i_end)
-	    break;
-
-	  start = i;
-	  other_start = j;
-
-	  for (;;)
-	    {
-	      /* Now find the end of this run of changes.  */
-
-	      while (i < i_end && changed[1+i]) i++;
-	      end = i;
-
-	      /* If the first changed line matches the following unchanged one,
-		 and this run does not follow right after a previous run,
-		 and there are no lines deleted from the other file here,
-		 then classify the first changed line as unchanged
-		 and the following line as changed in its place.  */
-
-	      /* You might ask, how could this run follow right after another?
-		 Only because the previous run was shifted here.  */
-
-	      if (end != i_end
-		  && equivs[start] == equivs[end]
-		  && !other_changed[1+j]
-		  && end != i_end
-		  && !((preceding >= 0 && start == preceding)
-		       || (other_preceding >= 0
-			   && other_start == other_preceding)))
-		{
-		  changed[1+end++] = true;
-		  changed[1+start++] = false;
-		  ++i;
-		  /* Since one line-that-matches is now before this run
-		     instead of after, we must advance in the other file
-		     to keep in synch.  */
-		  ++j;
-		}
-	      else
-		break;
-	    }
-
-	  preceding = i;
-	  other_preceding = j;
-	}
-    }
-
-    /** Number of elements (lines) in this file. */
-    final int buffered_lines;
-
-    /** IndexedSeq, indexed by line number, containing an equivalence code for
-       each line.  It is this IndexedSeq that is actually compared with that
-       of another file to generate differences. */
-    private final int[]	    equivs;
-
-    /** IndexedSeq, like the previous one except that
-       the elements for discarded lines have been squeezed out.  */
-    final int[]	   undiscarded;
-
-    /** IndexedSeq mapping virtual line numbers (not counting discarded lines)
-       to real ones (counting those lines).  Both are origin-0.  */
-    final int[]	   realindexes;
-
-    /** Total number of nondiscarded lines. */
-    int		    nondiscarded_lines;
-
-    /** Array, indexed by real origin-1 line number,
-       containing true for a line that is an insertion or a deletion.
-       The results of comparison are stored here.  */
-    boolean[]	    changed_flag;
-
-  }
-}
diff --git a/src/partest/scala/tools/partest/nest/DiffPrint.java b/src/partest/scala/tools/partest/nest/DiffPrint.java
deleted file mode 100644
index 31f9a1bc79..0000000000
--- a/src/partest/scala/tools/partest/nest/DiffPrint.java
+++ /dev/null
@@ -1,606 +0,0 @@
-
-package scala.tools.partest.nest;
-
-import java.io.*;
-import java.util.Vector;
-import java.util.Date;
-//import com.objectspace.jgl.predicates.UnaryPredicate;
-
-interface UnaryPredicate {
-  boolean execute(Object obj);
-}
-
-/** A simple framework for printing change lists produced by <code>Diff</code>.
-    @see bmsi.util.Diff
-    @author Stuart D. Gathman
-    Copyright (C) 2000 Business Management Systems, Inc.
-<p>
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation; either version 1, or (at your option)
-    any later version.
-<p>
-    This program 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 General Public License for more details.
-<p>
-    You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
- */
-public class DiffPrint {
-  /** A Base class for printing edit scripts produced by Diff.
-      This class divides the change list into "hunks", and calls
-      <code>print_hunk</code> for each hunk.  Various utility methods
-      are provided as well.
-   */
-  public static abstract class Base {
-    protected Base(Object[] a,Object[] b, Writer w) {
-      outfile = new PrintWriter(w);
-      file0 = a;
-      file1 = b;
-    }
-    /** Set to ignore certain kinds of lines when printing
-	an edit script.  For example, ignoring blank lines or comments.
-     */
-    protected UnaryPredicate ignore = null;
-
-    /** Set to the lines of the files being compared.
-     */
-    protected Object[] file0, file1;
-
-    /** Divide SCRIPT into pieces by calling HUNKFUN and
-       print each piece with PRINTFUN.
-       Both functions take one arg, an edit script.
-
-       PRINTFUN takes a subscript which belongs together (with a null
-       link at the end) and prints it.  */
-    public void print_script(Diff.change script) {
-      Diff.change next = script;
-
-      while (next != null)
-	{
-	  Diff.change t, end;
-
-	  /* Find a set of changes that belong together.  */
-	  t = next;
-	  end = hunkfun(next);
-
-	  /* Disconnect them from the rest of the changes,
-	     making them a hunk, and remember the rest for next iteration.  */
-	  next = end.link;
-	  end.link = null;
-	  //if (DEBUG)
-	  //  debug_script(t);
-
-	  /* Print this hunk.  */
-	  print_hunk(t);
-
-	  /* Reconnect the script so it will all be freed properly.  */
-	  end.link = next;
-	}
-	outfile.flush();
-    }
-
-    /** Called with the tail of the script
-       and returns the last link that belongs together with the start
-       of the tail. */
-
-    protected Diff.change hunkfun(Diff.change hunk) {
-      return hunk;
-    }
-
-    protected int first0, last0, first1, last1, deletes, inserts;
-    protected PrintWriter outfile;
-
-    /** Look at a hunk of edit script and report the range of lines in each file
-      that it applies to.  HUNK is the start of the hunk, which is a chain
-      of `struct change'.  The first and last line numbers of file 0 are stored
-      in *FIRST0 and *LAST0, and likewise for file 1 in *FIRST1 and *LAST1.
-      Note that these are internal line numbers that count from 0.
-
-      If no lines from file 0 are deleted, then FIRST0 is LAST0+1.
-
-      Also set *DELETES nonzero if any lines of file 0 are deleted
-      and set *INSERTS nonzero if any lines of file 1 are inserted.
-      If only ignorable lines are inserted or deleted, both are
-      set to 0.  */
-
-    protected void analyze_hunk(Diff.change hunk) {
-      int f0, l0 = 0, f1, l1 = 0, show_from = 0, show_to = 0;
-      int i;
-      Diff.change next;
-      boolean nontrivial = (ignore == null);
-
-      show_from = show_to = 0;
-
-      f0 = hunk.line0;
-      f1 = hunk.line1;
-
-      for (next = hunk; next != null; next = next.link)
-	{
-	  l0 = next.line0 + next.deleted - 1;
-	  l1 = next.line1 + next.inserted - 1;
-	  show_from += next.deleted;
-	  show_to += next.inserted;
-	  for (i = next.line0; i <= l0 && ! nontrivial; i++)
-	    if (!ignore.execute(file0[i]))
-	      nontrivial = true;
-	  for (i = next.line1; i <= l1 && ! nontrivial; i++)
-	    if (!ignore.execute(file1[i]))
-	      nontrivial = true;
-	}
-
-      first0 = f0;
-      last0 = l0;
-      first1 = f1;
-      last1 = l1;
-
-      /* If all inserted or deleted lines are ignorable,
-	 tell the caller to ignore this hunk.  */
-
-      if (!nontrivial)
-	show_from = show_to = 0;
-
-      deletes = show_from;
-      inserts = show_to;
-    }
-
-    /** Print the script header which identifies the files compared. */
-    protected void print_header(String filea, String fileb) { }
-
-    protected abstract void print_hunk(Diff.change hunk);
-
-    protected void print_1_line(String pre,Object linbuf) {
-      outfile.println(pre + linbuf.toString());
-    }
-
-    /** Print a pair of line numbers with SEPCHAR, translated for file FILE.
-       If the two numbers are identical, print just one number.
-
-       Args A and B are internal line numbers.
-       We print the translated (real) line numbers.  */
-
-    protected void print_number_range (char sepchar, int a, int b) {
-      /* Note: we can have B < A in the case of a range of no lines.
-	 In this case, we should print the line number before the range,
-	 which is B.  */
-      if (++b > ++a)
-	outfile.print("" + a + sepchar + b);
-      else
-	outfile.print(b);
-    }
-
-    public static char change_letter(int inserts, int deletes) {
-      if (inserts == 0)
-	return 'd';
-      else if (deletes == 0)
-	return 'a';
-      else
-	return 'c';
-    }
-  }
-
-  /** Print a change list in the standard diff format.
-   */
-  public static class NormalPrint extends Base {
-
-    public NormalPrint(Object[] a,Object[] b, Writer w) {
-      super(a,b,w);
-    }
-
-    /** Print a hunk of a normal diff.
-       This is a contiguous portion of a complete edit script,
-       describing changes in consecutive lines.  */
-
-    protected void print_hunk (Diff.change hunk) {
-
-      /* Determine range of line numbers involved in each file.  */
-      analyze_hunk(hunk);
-      if (deletes == 0 && inserts == 0)
-	return;
-
-      /* Print out the line number header for this hunk */
-      print_number_range (',', first0, last0);
-      outfile.print(change_letter(inserts, deletes));
-      print_number_range (',', first1, last1);
-      outfile.println();
-
-      /* Print the lines that the first file has.  */
-      if (deletes != 0)
-	for (int i = first0; i <= last0; i++)
-	  print_1_line ("< ", file0[i]);
-
-      if (inserts != 0 && deletes != 0)
-	outfile.println("---");
-
-      /* Print the lines that the second file has.  */
-      if (inserts != 0)
-	for (int i = first1; i <= last1; i++)
-	  print_1_line ("> ", file1[i]);
-    }
-  }
-
-  /** Prints an edit script in a format suitable for input to <code>ed</code>.
-      The edit script must be generated with the reverse option to
-      be useful as actual <code>ed</code> input.
-   */
-  public static class EdPrint extends Base {
-
-    public EdPrint(Object[] a,Object[] b, Writer w) {
-      super(a,b,w);
-    }
-
-    /** Print a hunk of an ed diff */
-    protected void print_hunk(Diff.change hunk) {
-
-      /* Determine range of line numbers involved in each file.  */
-      analyze_hunk (hunk);
-      if (deletes == 0 && inserts == 0)
-	return;
-
-      /* Print out the line number header for this hunk */
-      print_number_range (',', first0, last0);
-      outfile.println(change_letter(inserts, deletes));
-
-      /* Print new/changed lines from second file, if needed */
-      if (inserts != 0)
-	{
-	  boolean inserting = true;
-	  for (int i = first1; i <= last1; i++)
-	    {
-	      /* Resume the insert, if we stopped.  */
-	      if (! inserting)
-		outfile.println(i - first1 + first0 + "a");
-	      inserting = true;
-
-	      /* If the file's line is just a dot, it would confuse `ed'.
-		 So output it with a double dot, and set the flag LEADING_DOT
-		 so that we will output another ed-command later
-		 to change the double dot into a single dot.  */
-
-	      if (".".equals(file1[i]))
-		{
-		  outfile.println("..");
-		  outfile.println(".");
-		  /* Now change that double dot to the desired single dot.  */
-		  outfile.println(i - first1 + first0 + 1 + "s/^\\.\\././");
-		  inserting = false;
-		}
-	      else
-		/* Line is not `.', so output it unmodified.  */
-		print_1_line ("", file1[i]);
-	    }
-
-	  /* End insert mode, if we are still in it.  */
-	  if (inserting)
-	    outfile.println(".");
-	}
-    }
-  }
-
-  /** Prints an edit script in context diff format.  This and its
-    'unified' variation is used for source code patches.
-   */
-  public static class ContextPrint extends Base {
-
-    protected int context = 3;
-
-    public ContextPrint(Object[] a,Object[] b, Writer w) {
-      super(a,b,w);
-    }
-
-    protected void print_context_label (String mark, File inf, String label) {
-      if (label != null)
-	outfile.println(mark + ' ' + label);
-      else if (inf.lastModified() > 0)
-        // FIXME: use DateFormat to get precise format needed.
-	outfile.println(
-	  mark + ' ' + inf.getPath() + '\t' + new Date(inf.lastModified())
-	);
-      else
-	/* Don't pretend that standard input is ancient.  */
-	outfile.println(mark + ' ' + inf.getPath());
-    }
-
-    public void print_header(String filea,String fileb) {
-      print_context_label ("***", new File(filea), filea);
-      print_context_label ("---", new File(fileb), fileb);
-    }
-
-    /** If function_regexp defined, search for start of function. */
-    private String find_function(Object[] lines, int start) {
-      return null;
-    }
-
-    protected void print_function(Object[] file,int start) {
-      String function = find_function (file0, first0);
-      if (function != null) {
-	outfile.print(" ");
-	outfile.print(
-	  (function.length() < 40) ? function : function.substring(0,40)
-	);
-      }
-    }
-
-    protected void print_hunk(Diff.change hunk) {
-
-      /* Determine range of line numbers involved in each file.  */
-
-      analyze_hunk (hunk);
-
-      if (deletes == 0 && inserts == 0)
-	return;
-
-      /* Include a context's width before and after.  */
-
-      first0 = Math.max(first0 - context, 0);
-      first1 = Math.max(first1 - context, 0);
-      last0 = Math.min(last0 + context, file0.length - 1);
-      last1 = Math.min(last1 + context, file1.length - 1);
-
-
-      outfile.print("***************");
-
-      /* If we looked for and found a function this is part of,
-	 include its name in the header of the diff section.  */
-      print_function (file0, first0);
-
-      outfile.println();
-      outfile.print("*** ");
-      print_number_range (',', first0, last0);
-      outfile.println(" ****");
-
-      if (deletes != 0) {
-	Diff.change next = hunk;
-
-	for (int i = first0; i <= last0; i++) {
-	  /* Skip past changes that apply (in file 0)
-	     only to lines before line I.  */
-
-	  while (next != null && next.line0 + next.deleted <= i)
-	    next = next.link;
-
-	  /* Compute the marking for line I.  */
-
-	  String prefix = " ";
-	  if (next != null && next.line0 <= i)
-	    /* The change NEXT covers this line.
-	       If lines were inserted here in file 1, this is "changed".
-	       Otherwise it is "deleted".  */
-	    prefix = (next.inserted > 0) ? "!" : "-";
-
-	  print_1_line (prefix, file0[i]);
-	}
-      }
-
-      outfile.print("--- ");
-      print_number_range (',', first1, last1);
-      outfile.println(" ----");
-
-      if (inserts != 0) {
-	Diff.change next = hunk;
-
-	for (int i = first1; i <= last1; i++) {
-	  /* Skip past changes that apply (in file 1)
-	     only to lines before line I.  */
-
-	  while (next != null && next.line1 + next.inserted <= i)
-	    next = next.link;
-
-	  /* Compute the marking for line I.  */
-
-	  String prefix = " ";
-	  if (next != null && next.line1 <= i)
-	    /* The change NEXT covers this line.
-	       If lines were deleted here in file 0, this is "changed".
-	       Otherwise it is "inserted".  */
-	    prefix = (next.deleted > 0) ? "!" : "+";
-
-	  print_1_line (prefix, file1[i]);
-	}
-      }
-    }
-  }
-
-  /** Prints an edit script in context diff format.  This and its
-    'unified' variation is used for source code patches.
-   */
-  public static class UnifiedPrint extends ContextPrint {
-
-    public UnifiedPrint(Object[] a,Object[] b, Writer w) {
-      super(a,b,w);
-    }
-
-    public void print_header(String filea,String fileb) {
-      print_context_label ("---", new File(filea), filea);
-      print_context_label ("+++", new File(fileb), fileb);
-    }
-
-    private void print_number_range (int a, int b) {
-      //translate_range (file, a, b, &trans_a, &trans_b);
-
-      /* Note: we can have B < A in the case of a range of no lines.
-	 In this case, we should print the line number before the range,
-	 which is B.  */
-      if (b < a)
-	outfile.print(b + ",0");
-      else
-        super.print_number_range(',',a,b);
-    }
-
-    protected void print_hunk(Diff.change hunk) {
-      /* Determine range of line numbers involved in each file.  */
-      analyze_hunk (hunk);
-
-      if (deletes == 0 && inserts == 0)
-	return;
-
-      /* Include a context's width before and after.  */
-
-      first0 = Math.max(first0 - context, 0);
-      first1 = Math.max(first1 - context, 0);
-      last0 = Math.min(last0 + context, file0.length - 1);
-      last1 = Math.min(last1 + context, file1.length - 1);
-
-
-
-      outfile.print("@@ -");
-      print_number_range (first0, last0);
-      outfile.print(" +");
-      print_number_range (first1, last1);
-      outfile.print(" @@");
-
-      /* If we looked for and found a function this is part of,
-	 include its name in the header of the diff section.  */
-      print_function(file0,first0);
-
-      outfile.println();
-
-      Diff.change next = hunk;
-      int i = first0;
-      int j = first1;
-
-      while (i <= last0 || j <= last1) {
-
-	/* If the line isn't a difference, output the context from file 0. */
-
-	if (next == null || i < next.line0) {
-	  outfile.print(' ');
-	  print_1_line ("", file0[i++]);
-	  j++;
-	}
-	else {
-	  /* For each difference, first output the deleted part. */
-
-	  int k = next.deleted;
-	  while (k-- > 0) {
-	    outfile.print('-');
-	    print_1_line ("", file0[i++]);
-	  }
-
-	  /* Then output the inserted part. */
-
-	  k = next.inserted;
-	  while (k-- > 0) {
-	    outfile.print('+');
-	    print_1_line ("", file1[j++]);
-	  }
-
-	  /* We're done with this hunk, so on to the next! */
-
-	  next = next.link;
-	}
-      }
-    }
-  }
-
-
-  /** Read a text file into an array of String.  This provides basic diff
-     functionality.  A more advanced diff utility will use specialized
-     objects to represent the text lines, with options to, for example,
-     convert sequences of whitespace to a single space for comparison
-     purposes.
-   */
-  static String[] slurp(String file) throws IOException {
-    BufferedReader rdr = new BufferedReader(new FileReader(file));
-    Vector<String> s = new Vector<String>();
-    for (;;) {
-      String line = rdr.readLine();
-      if (line == null) break;
-      s.addElement(line);
-    }
-    String[] a = new String[s.size()];
-    s.copyInto(a);
-    return a;
-  }
-
-  public static void main(String[] argv) throws IOException {
-    String filea = argv[argv.length - 2];
-    String fileb = argv[argv.length - 1];
-    String[] a = slurp(filea);
-    String[] b = slurp(fileb);
-    Diff d = new Diff(a,b);
-    char style = 'n';
-    for (int i = 0; i < argv.length - 2; ++i) {
-      String f = argv[i];
-      if (f.startsWith("-")) {
-        for (int j = 1; j < f.length(); ++j) {
-	  switch (f.charAt(j)) {
-	  case 'e':	// Ed style
-	    style = 'e'; break;
-	  case 'c':	// Context diff
-	    style = 'c'; break;
-	  case 'u':
-	    style = 'u'; break;
-	  }
-	}
-      }
-    }
-    boolean reverse = style == 'e';
-    Diff.change script = d.diff_2(reverse);
-    if (script == null)
-      System.err.println("No differences");
-    else {
-      Base p;
-      Writer w = new OutputStreamWriter(System.out);
-      switch (style) {
-      case 'e':
-        p = new EdPrint(a,b,w); break;
-      case 'c':
-        p = new ContextPrint(a,b,w); break;
-      case 'u':
-        p = new UnifiedPrint(a,b,w); break;
-      default:
-        p = new NormalPrint(a,b,w);
-      }
-      p.print_header(filea,fileb);
-      p.print_script(script);
-    }
-  }
-
-  public static void doDiff(String[] argv, Writer w) throws IOException {
-    String filea = argv[argv.length - 2];
-    String fileb = argv[argv.length - 1];
-    String[] a = slurp(filea);
-    String[] b = slurp(fileb);
-    Diff d = new Diff(a,b);
-    char style = 'n';
-    for (int i = 0; i < argv.length - 2; ++i) {
-      String f = argv[i];
-      if (f.startsWith("-")) {
-        for (int j = 1; j < f.length(); ++j) {
-	  switch (f.charAt(j)) {
-	  case 'e':	// Ed style
-	    style = 'e'; break;
-	  case 'c':	// Context diff
-	    style = 'c'; break;
-	  case 'u':
-	    style = 'u'; break;
-	  }
-	}
-      }
-    }
-    boolean reverse = style == 'e';
-    Diff.change script = d.diff_2(reverse);
-    if (script == null)
-      w.write("No differences\n");
-    else {
-      Base p;
-      switch (style) {
-      case 'e':
-        p = new EdPrint(a,b,w); break;
-      case 'c':
-        p = new ContextPrint(a,b,w); break;
-      case 'u':
-        p = new UnifiedPrint(a,b,w); break;
-      default:
-        p = new NormalPrint(a,b,w);
-      }
-      p.print_header(filea,fileb);
-      p.print_script(script);
-    }
-  }
-
-}
diff --git a/src/partest/scala/tools/partest/nest/FileManager.scala b/src/partest/scala/tools/partest/nest/FileManager.scala
index 2823967ecf..70fdb33c6a 100644
--- a/src/partest/scala/tools/partest/nest/FileManager.scala
+++ b/src/partest/scala/tools/partest/nest/FileManager.scala
@@ -18,34 +18,31 @@ import scala.collection.mutable
 
 trait FileUtil {
   /**
-   * Compares two files using a Java implementation of the GNU diff
-   * available at http://www.bmsi.com/java/#diff.
+   * Compares two files using difflib to produce a unified diff.
    *
    * @param  f1  the first file to be compared
    * @param  f2  the second file to be compared
-   * @return the text difference between the compared files
+   * @return the unified diff of the compared files or the empty string if they're equal
    */
   def compareFiles(f1: File, f2: File): String = {
-    val diffWriter = new StringWriter
-    val args = Array(f1.getAbsolutePath(), f2.getAbsolutePath())
-
-    DiffPrint.doDiff(args, diffWriter)
-    val res = diffWriter.toString
-    if (res startsWith "No") "" else res
+    compareContents(io.Source.fromFile(f1).getLines.toSeq, io.Source.fromFile(f2).getLines.toSeq, f1.getName, f2.getName)
   }
-  def compareContents(lines1: Seq[String], lines2: Seq[String]): String = {
-    val xs1 = lines1.toArray[AnyRef]
-    val xs2 = lines2.toArray[AnyRef]
-
-    val diff   = new Diff(xs1, xs2)
-    val change = diff.diff_2(false)
-    val writer = new StringWriter
-    val p      = new DiffPrint.NormalPrint(xs1, xs2, writer)
-
-    p.print_script(change)
-    val res = writer.toString
-    if (res startsWith "No ") ""
-    else res
+
+  /**
+   * Compares two lists of lines using difflib to produce a unified diff.
+   *
+   * @param  origLines  the first seq of lines to be compared
+   * @param  newLines   the second seq of lines to be compared
+   * @param  origName   file name to be used in unified diff for `origLines`
+   * @param  newName    file name to be used in unified diff for `newLines`
+   * @return the unified diff of the `origLines` and `newLines` or the empty string if they're equal
+   */
+  def compareContents(origLines: Seq[String], newLines: Seq[String], origName: String = "a", newName: String = "b"): String = {
+    import collection.JavaConverters._
+
+    val diff = difflib.DiffUtils.diff(origLines.asJava, newLines.asJava)
+    if (diff.getDeltas.isEmpty) ""
+    else difflib.DiffUtils.generateUnifiedDiff(origName, newName, origLines.asJava, diff, 1).asScala.mkString("\n")
   }
 }
 object FileUtil extends FileUtil { }
diff --git a/src/partest/scala/tools/partest/nest/PathSettings.scala b/src/partest/scala/tools/partest/nest/PathSettings.scala
index a42c2219b1..dfa1187691 100644
--- a/src/partest/scala/tools/partest/nest/PathSettings.scala
+++ b/src/partest/scala/tools/partest/nest/PathSettings.scala
@@ -72,6 +72,9 @@ object PathSettings {
     findJar(buildPackLibDir.files ++ srcLibDir.files, "scalacheck") getOrElse {
       sys.error("No scalacheck jar found in '%s' or '%s'".format(buildPackLibDir, srcLibDir))
     }
+
+  lazy val diffUtils: File =
+    findJar(buildPackLibDir.files, "diffutils-1.3.0") getOrElse sys.error(s"No diffutils-1.3.0.jar found in '$buildPackLibDir'.")
 }
 
 class PathSettings() {
diff --git a/src/partest/scala/tools/partest/nest/ReflectiveRunner.scala b/src/partest/scala/tools/partest/nest/ReflectiveRunner.scala
index 5cb8589d66..700667afcf 100644
--- a/src/partest/scala/tools/partest/nest/ReflectiveRunner.scala
+++ b/src/partest/scala/tools/partest/nest/ReflectiveRunner.scala
@@ -53,13 +53,14 @@ class ReflectiveRunner {
       Array(latestCompFile, latestReflectFile, latestLibFile, latestPartestFile, latestFjbgFile, latestScalapFile, latestActorsFile) map (x => io.File(x))
 
     val sepUrls   = files map (_.toURL)
+    // this seems to be the core classloader that determines which classes can be found when running partest from the test/partest script
     var sepLoader = new URLClassLoader(sepUrls, null)
 
     // this is a workaround for https://issues.scala-lang.org/browse/SI-5433
-    // when that bug is fixed, this paragraph of code can be safely removed
     // we hack into the classloader that will become parent classloader for scalac
     // this way we ensure that reflective macro lookup will pick correct Code.lift
-    sepLoader = new URLClassLoader((PathSettings.srcCodeLib +: files) map (_.toURL), null)
+    // it's also used to inject diffutils into the classpath when running partest from the test/partest script
+    sepLoader = new URLClassLoader((PathSettings.srcCodeLib +: (PathSettings.diffUtils +: files)) map (_.toURL), null)
 
     if (isPartestDebug)
       println("Loading classes from:\n" + sepUrls.mkString("\n"))
diff --git a/src/partest/scala/tools/partest/nest/RunnerManager.scala b/src/partest/scala/tools/partest/nest/RunnerManager.scala
index 0d979d2692..f80f6f38fd 100644
--- a/src/partest/scala/tools/partest/nest/RunnerManager.scala
+++ b/src/partest/scala/tools/partest/nest/RunnerManager.scala
@@ -79,6 +79,7 @@ class RunnerManager(kind: String, val fileManager: FileManager, params: TestRunP
 
   val compileMgr = new CompileManager(fileManager)
   fileManager.CLASSPATH += File.pathSeparator + PathSettings.scalaCheck
+  fileManager.CLASSPATH += File.pathSeparator + PathSettings.diffUtils // needed to put diffutils on test/partest's classpath
 
   private def compareFiles(f1: File, f2: File): String =
     try fileManager.compareFiles(f1, f2)