Generate unified diff style reject files.

---
 patch.c                          |  104 +++++++++++++++++++++++++++++++++++++--
 patch.man                        |    3 +
 tests/unified-reject-files.shrun |  104 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 208 insertions(+), 3 deletions(-)

Index: b/patch.man
===================================================================
--- a/patch.man
+++ b/patch.man
@@ -517,6 +517,9 @@ instead of the default
 .B \&.rej
 file.
 .TP
+\fB\*=unified\-reject\-files\fP
+Produce unified reject files. The default is to produce context type reject files.
+.TP
 \fB\-R\fP  or  \fB\*=reverse\fP
 Assume that this patch was created with the old and new files swapped.
 (Yes, I'm afraid that does happen occasionally, human nature being what it
Index: b/patch.c
===================================================================
--- a/patch.c
+++ b/patch.c
@@ -66,8 +66,9 @@ static bool patch_match (LINENUM, LINENU
 static bool similar (char const *, size_t, char const *, size_t);
 static bool spew_output (struct outstate *);
 static char const *make_temp (char);
+static void abort_hunk_context (void);
+static void abort_hunk_unified (void);
 static int numeric_string (char const *, bool, char const *);
-static void abort_hunk (void);
 static void cleanup (void);
 static void get_some_switches (void);
 static void init_output (char const *, int, struct outstate *);
@@ -76,6 +77,8 @@ static void reinitialize_almost_everythi
 static void remove_if_needed (char const *, int volatile *);
 static void usage (FILE *, int) __attribute__((noreturn));
 
+static void (*abort_hunk) (void) = abort_hunk_context;
+
 static bool make_backups;
 static bool backup_if_mismatch;
 static char const *version_control;
@@ -522,6 +525,7 @@ static struct option const longopts[] =
   {"no-backup-if-mismatch", no_argument, NULL, CHAR_MAX + 6},
   {"posix", no_argument, NULL, CHAR_MAX + 7},
   {"quoting-style", required_argument, NULL, CHAR_MAX + 8},
+  {"unified-reject-files", no_argument, NULL, CHAR_MAX + 9},
   {NULL, no_argument, NULL, 0}
 };
 
@@ -580,6 +584,7 @@ static char const *const option_help[] =
 "  --verbose  Output extra information about the work being done.",
 "  --dry-run  Do not actually change any files; just print what would happen.",
 "  --posix  Conform to the POSIX standard.",
+"  --unified-reject-files  Create unified reject files.",
 "",
 "  -d DIR  --directory=DIR  Change the working directory to DIR first.",
 #if HAVE_SETMODE_DOS
@@ -779,6 +784,9 @@ get_some_switches (void)
 				     (enum quoting_style) i);
 		}
 		break;
+	    case CHAR_MAX + 9:
+		abort_hunk = abort_hunk_unified;
+		break;
 	    default:
 		usage (stderr, 2);
 	}
@@ -930,7 +938,7 @@ locate_hunk (LINENUM fuzz)
 /* We did not find the pattern, dump out the hunk so they can handle it. */
 
 static void
-abort_hunk (void)
+abort_hunk_context (void)
 {
     register LINENUM i;
     register LINENUM pat_end = pch_end ();
@@ -979,13 +987,103 @@ abort_hunk (void)
 	    pch_write_line (i, rejfp);
 	    break;
 	default:
-	    fatal ("fatal internal error in abort_hunk");
+	    fatal ("fatal internal error in abort_hunk_context");
 	}
 	if (ferror (rejfp))
 	  write_fatal ();
     }
 }
 
+/* Produce unified reject files */
+
+static void
+print_unified(FILE *fp)
+{
+    register LINENUM old = 1;
+    register LINENUM lastline = pch_ptrn_lines ();
+    register LINENUM new = lastline + 1;
+    register LINENUM pat_end = pch_end ();
+
+    while (pch_char (new) == '=' || pch_char (new) == '\n')
+      new++;
+
+    while (old <= lastline)
+      {
+	if (pch_char (old) == '-')
+	  {
+	    fputc ('-', fp);
+	    pch_write_line (old++, fp);
+	  }
+	else if (new > pat_end)
+	    break;
+	else if (pch_char (new) == '+')
+	  {
+	    fputc ('+', fp);
+	    pch_write_line (new++, fp);
+	  }
+	else if (pch_char (new) != pch_char (old))
+	  {
+	    char numbuf0[LINENUM_LENGTH_BOUND + 1];
+	    char numbuf1[LINENUM_LENGTH_BOUND + 1];
+	    if (debug & 1)
+	      say ("oldchar = '%c', newchar = '%c'\n",
+		   pch_char (old), pch_char (new));
+	    fatal ("Out-of-sync patch, lines %s,%s -- mangled text or "
+	    	   "line numbers, maybe?",
+		   format_linenum (numbuf0, pch_hunk_beg () + old),
+		   format_linenum (numbuf1, pch_hunk_beg () + new));
+	  }
+	else if (pch_char (new) == '!')
+	  {
+	    do
+	      {
+		fputc ('-', fp);
+		pch_write_line (old++, fp);
+	      }
+	    while (pch_char (old) == '!');
+	    do
+	      {
+		fputc ('+', fp);
+		pch_write_line (new++, fp);
+	      }
+	    while (pch_char (new) == '!');
+	  }
+	else
+	  {
+	    assert (pch_char (new) == ' ');
+	    fputc (' ', fp);
+	    pch_write_line (new, fp);
+	    old++;
+	    new++;
+	  }
+      }
+    while (pch_char (new) == '+' || pch_char (new) == ' ')
+      {
+	fputc ('+', fp);
+	pch_write_line (new++, fp);
+      }
+    assert (new > pat_end);
+}
+
+static void
+abort_hunk_unified (void)
+{
+    char rangebuf0[LINERANGE_LENGTH_BOUND + 1];
+    char rangebuf1[LINERANGE_LENGTH_BOUND + 1];
+    LINENUM oldfirst = pch_first () + last_offset;
+    LINENUM newfirst = pch_newfirst () + last_offset;
+    char const *c_function = pch_c_function ();
+
+    fprintf (rejfp, "@@ -%s +%s @@%s\n",
+	     format_startcount (rangebuf0, oldfirst, pch_ptrn_lines ()),
+	     format_startcount (rangebuf1, newfirst, pch_repl_lines ()),
+	     c_function ? c_function : "");
+    print_unified (rejfp);
+
+    if (ferror (rejfp))
+      write_fatal ();
+}
+
 /* We found where to apply it (we hope), so do it. */
 
 static bool
Index: b/tests/unified-reject-files.shrun
===================================================================
--- /dev/null
+++ b/tests/unified-reject-files.shrun
@@ -0,0 +1,104 @@
+$ PATCH=$(pwd)/patch
+$ tmpdir=$(mktemp -d)
+$ trap "cd /; rm -rf $tmpdir" EXIT
+$ cd $tmpdir
+$ cat > f.orig
+< a() {
+< 2
+< 3
+<
+< 5
+< 6
+< }
+
+$ sed -e 's/5/5a/' f.orig > f
+$ diff -U0 -p \
++      -L "f.orig	2009-02-07 14:49:02.000000000 +0100" \
++      -L "f	2009-02-07 14:49:03.000000000 +0100" \
++      f.orig f > f.diff
+
+$ $PATCH -f -F0 -s --no-backup-if-mismatch f < f.diff
+> 1 out of 1 hunk FAILED -- saving rejects to file f.rej
+
+Note: patch cannot deal with nanosecond timestamps :-(
+
+$ cat f.rej
+> *************** a() {
+> *** 5 ****
+> - 5
+> --- 5 ----
+> + 5a
+
+$ diff -U0 -p -L f.orig -L f f.orig f > f.diff
+$ $PATCH -f -F0 -s --no-backup-if-mismatch --unified-reject-files f < f.diff
+> 1 out of 1 hunk FAILED -- saving rejects to file f.rej
+
+$ cat f.rej
+> @@ -5 +5 @@ a() {
+> -5
+> +5a
+
+$ $PATCH -f -F0 -s --no-backup-if-mismatch f < f.diff
+> 1 out of 1 hunk FAILED -- saving rejects to file f.rej
+
+$ cat f.rej
+> *************** a() {
+> *** 5 ****
+> - 5
+> --- 5 ----
+> + 5a
+
+$ $PATCH -f -F0 -s --no-backup-if-mismatch --unified-reject-files -R f.orig < f.diff
+> 1 out of 1 hunk FAILED -- saving rejects to file f.orig.rej
+
+$ cat f.orig.rej
+> @@ -5 +5 @@ a() {
+> -5a
+> +5
+
+$ diff -U2 -p -L f.orig -L f f.orig f > f.diff
+$ sed -e 's/5/5a/' -e 's/6/6x/' f.orig > f
+$ $PATCH -F0 -s --no-backup-if-mismatch --unified-reject-files f < f.diff
+> 1 out of 1 hunk FAILED -- saving rejects to file f.rej
+
+$ cat f.rej
+> @@ -3,5 +3,5 @@ a() {
+>  3
+>  
+> -5
+> +5a
+>  6
+>  }
+
+$ $PATCH -F0 -s --no-backup-if-mismatch f < f.diff
+> 1 out of 1 hunk FAILED -- saving rejects to file f.rej
+
+$ cat f.rej
+> *************** a() {
+> *** 3,7 ****
+>   3
+>   
+> - 5
+>   6
+>   }
+> --- 3,7 ----
+>   3
+>   
+> + 5a
+>   6
+>   }
+
+$ diff -Nu -p -L /dev/null -L f.orig /dev/null f.orig > f2.diff
+$ $PATCH -F0 -s --no-backup-if-mismatch --unified-reject-files f --set-utc < f2.diff
+> Patch attempted to create file f, which already exists.
+> 1 out of 1 hunk FAILED -- saving rejects to file f.rej
+
+$ cat f.rej
+> @@ -0,0 +1,7 @@
+> +a() {
+> +2
+> +3
+> +
+> +5
+> +6
+> +}