Re: [Monotone-devel] Re: Non-modal merge

[Ralf S. Engelschall]

On Mon, Sep 24, 2007, Stefan Monnier wrote:

> [...]
> > I've not found an option combination for diff3(1)
> > which shows the ancestors but not the non-overlapping parts. I've tried
> > many combinations of --merge, -A, -E, -x and -X but have not found a
> > solution.
>
> Indeed AFAIK there's no such solution.  It's easy to change diff3 to provide
> this feature, and I proposed such a change to diff3's maintainer about 10
> years ago, but I didn't have a clean patch back then and never got around to
> write one.

Ok, as I really want the most useful workspace-based merging for
Monotone myself, I've investigated on this issue for us and crafted such
a patch against GNU diffutils 2.8.7 -- I've now even already applied it
to our official OpenPKG "diffutils" package, so I've it available in the
OpenPKG world ;-) I append you the patch here, too...

                                       Ralf S. Engelschall
                                       address@hidden
                                       www.engelschall.com

Add option "-O" to diff3(1) in order to allow one to display information
about the 2nd file (the ancestor/older one) not just under option "-A",
but also under "-E" and "-X". This way one especially can get the
consise output of "-E" (where only "unmerged" conflicts and overlaps are
shown), but still get the verbose information (introduced with "|||||||
<older-name>") about the ancestor/older file in the flagged/marked
output. This way "diff3 -m -E -O" gives one the best resolution chances
on a 3-way merge without having to deal with the useless (already
"merged") information one would get under "diff3 -m -A". --rse 20070924

Index: man/diff3.1
--- man/diff3.1.orig    2004-04-13 09:07:28 +0200
+++ man/diff3.1 2007-09-24 21:42:43 +0200
@@ -38,6 +38,9 @@
 \fB\-a\fR  \fB\-\-text\fR
 Treat all files as text.
 .TP
+\fB\-O\fR
+Always show content of OLDFILE in bracketing output of unmerged changes.
+.TP
 \fB\-\-strip\-trailing\-cr\fR
 Strip trailing carriage return on input.
 .TP
Index: src/diff3.c
--- src/diff3.c.orig    2004-04-12 09:44:35 +0200
+++ src/diff3.c 2007-09-24 21:21:38 +0200
@@ -153,6 +153,9 @@
 /* If nonzero, show information for DIFF_2ND diffs.  */
 static bool show_2nd;

+/* If nonzero, show information for DIFF_2ND on overlaps, too. */
+static bool show_2nd_on_overlap;
+
 /* If nonzero, include `:wq' at the end of the script
    to write out the file being edited.   */
 static bool finalwrite;
@@ -234,7 +237,7 @@
   textdomain (PACKAGE);
   c_stack_action (0);

-  while ((c = getopt_long (argc, argv, "aeimvx3AEL:TX", longopts, 0)) != -1)
+  while ((c = getopt_long (argc, argv, "aeimvx3AEL:TXO", longopts, 0)) != -1)
     {
       switch (c)
        {
@@ -269,6 +272,9 @@
        case 'e':
          incompat++;
          break;
+       case 'O':
+         show_2nd_on_overlap = true;
+         break;
        case 'T':
          initial_tab = true;
          break;
@@ -1527,7 +1533,7 @@
          leading_dot = false;
          if (type == DIFF_ALL)
            {
-             if (show_2nd)
+             if (show_2nd || show_2nd_on_overlap)
                {
                  /* Append lines from FILE1.  */
                  fprintf (outputfile, "||||||| %s\n", file1);
@@ -1665,7 +1671,7 @@
                        D_RELLEN (b, mapping[FILE0], i), outputfile);
            }

-         if (show_2nd)
+         if (show_2nd || show_2nd_on_overlap)
            {
              /* Put in lines from FILE1 with bracket.  */
              fprintf (outputfile, format_2nd, file1);