Latest from Cyclic Software

1 files changed, 44 insertions, 23 deletions

diff --git a/gnu/usr.bin/cvs/diff/diff3.c b/gnu/usr.bin/cvs/diff/diff3.c
index 2f05d165fc9..4a6fba618c2 100644
--- a/gnu/usr.bin/cvs/diff/diff3.c
+++ b/gnu/usr.bin/cvs/diff/diff3.c
@@ -171,7 +171,7 @@ static int edscript;
 static int flagging;
 
 /* Number of lines to keep in identical prefix and suffix.  */
-static int horizon_lines = 10;
+static int const horizon_lines = 10;
 
 /* Use a tab to align output lines (-T).  */
 static int tab_align_flag;
@@ -370,28 +370,44 @@ diff3_run (argc, argv, out, callbacks_arg)
      file0-file1 diffs didn't line up with the file0-file2 diffs
      (which is entirely possible since we don't use diff's -n option),
      diff3 might report phantom changes from file1 to file2.  */
+  /* Also try to compare file0 to file1 because this is the where
+     changes are expected to come from.  Diffing between these pairs
+     of files is is most likely to return the intended changes.  There
+     can also be the same problem with phantom changes from file0 to
+     file1. */
+  /* Historically, the default common file was file2.  Ediff for emacs
+     and possibly other applications, have therefore made file2 the
+     ancestor.  So, for compatibility, if this is simply a three
+     way diff (not a merge or edscript) then use the old way with
+     file2 as the common file. */
+
+  {
+    int common;
+    if (edscript || merge )
+      {
+	common = 1;
+      }
+    else
+      {
+	common = 2;
+      }
+    if (strcmp (file[common], "-") == 0)
+      {
+	/* Sigh.  We've got standard input as the arg corresponding to
+	   the desired common file.  We can't call diff twice on
+	   stdin.  Use another arg as the common file instead.  */
+	common = 3 - common;
+	if (strcmp (file[0], "-") == 0 || strcmp (file[common], "-") == 0)
+	  {
+	    diff_error ("%s", "`-' specified for more than one input file", 0);
+	    return 2;
+	  }
+      }
 
-  if (strcmp (file[2], "-") == 0)
-    {
-      /* Sigh.  We've got standard input as the last arg.  We can't
-	 call diff twice on stdin.  Use the middle arg as the common
-	 file instead.  */
-      if (strcmp (file[0], "-") == 0 || strcmp (file[1], "-") == 0)
-        {
-	  diff_error ("%s", "`-' specified for more than one input file", 0);
-	  return 2;
-        }
-      mapping[0] = 0;
-      mapping[1] = 2;
-      mapping[2] = 1;
-    }
-  else
-    {
-      /* Normal, what you'd expect */
-      mapping[0] = 0;
-      mapping[1] = 1;
-      mapping[2] = 2;
-    }
+    mapping[0] = 0;
+    mapping[1] = 3 - common;
+    mapping[2] = common;
+  }
 
   for (i = 0; i < 3; i++)
     rev_mapping[mapping[i]] = i;
@@ -444,12 +460,18 @@ diff3_run (argc, argv, out, callbacks_arg)
   commonname = file[rev_mapping[FILEC]];
   thread1 = process_diff (file[rev_mapping[FILE1]], commonname, &last_block,
 			  &content1);
+  /* What is the intention behind determining horizon_lines from first
+     diff?  I think it is better to use the same parameters for each
+     diff so that equal differences in each diff will appear the
+     same. */
+  /*
   if (thread1)
     for (i = 0; i < 2; i++)
       {
 	horizon_lines = max (horizon_lines, D_NUMLINES (thread1, i));
 	horizon_lines = max (horizon_lines, D_NUMLINES (last_block, i));
       }
+  */
   thread0 = process_diff (file[rev_mapping[FILE0]], commonname, &last_block,
 			  &content0);
   diff3 = make_3way_diff (thread0, thread1);
@@ -1855,7 +1877,6 @@ initialize_main (argcp, argvp)
   always_text = 0;
   edscript = 0;
   flagging = 0;
-  horizon_lines = 10;
   tab_align_flag = 0;
   simple_only = 0;
   overlap_only = 0;