This patch allows multiple --compare-dest or --link-dest options to be
used, making the transfer of some files more optimal.  Note that the
algorithm does NOT search for the best match -- it stops at the first
match and uses that as the basis file for the transfer, so be sure to
order your arguments appropriately.

--- generator.c	23 Jun 2004 16:51:21 -0000	1.89
+++ generator.c	23 Jun 2004 17:29:39 -0000
@@ -42,7 +42,7 @@ extern int size_only;
 extern int io_timeout;
 extern int protocol_version;
 extern int always_checksum;
-extern char *compare_dest;
+extern char *compare_dest[];
 extern int link_dest;
 extern int whole_file;
 extern int local_server;
@@ -80,13 +80,12 @@ static int skip_file(char *fname, struct
 	if (always_checksum && S_ISREG(st->st_mode)) {
 		char sum[MD4_SUM_LENGTH];
 		char fnamecmpdest[MAXPATHLEN];
+		int i;
 
-		if (compare_dest != NULL) {
-			if (access(fname, 0) != 0) {
-				pathjoin(fnamecmpdest, sizeof fnamecmpdest,
-					 compare_dest, fname);
-				fname = fnamecmpdest;
-			}
+		for (i = 0; compare_dest[i] != NULL && access(fname, 0) < 0; i++) {
+			pathjoin(fnamecmpdest, sizeof fnamecmpdest,
+					compare_dest[i], fname);
+			fname = fnamecmpdest;
 		}
 		file_checksum(fname,sum,st->st_size);
 		return memcmp(sum, file->u.sum, protocol_version < 21 ? 2
@@ -423,13 +422,18 @@ void recv_generator(char *fname, struct 
 
 	fnamecmp = fname;
 
-	if (statret == -1 && compare_dest != NULL) {
+	if (statret == -1 && compare_dest[0] != NULL) {
 		/* try the file at compare_dest instead */
 		int saveerrno = errno;
-		pathjoin(fnamecmpbuf, sizeof fnamecmpbuf, compare_dest, fname);
-		statret = link_stat(fnamecmpbuf, &st, 0);
-		if (!S_ISREG(st.st_mode))
-			statret = -1;
+		int i;
+		for (i = 0; compare_dest[i] != NULL; i++) {
+			pathjoin(fnamecmpbuf, sizeof fnamecmpbuf, compare_dest[i], fname);
+			if ((statret = link_stat(fnamecmpbuf, &st, 0)) == 0) {
+				if (S_ISREG(st.st_mode))
+					break;
+				statret = -1;
+			}
+		}
 		if (statret == -1)
 			errno = saveerrno;
 #if HAVE_LINK
--- options.c	20 Jun 2004 19:47:05 -0000	1.157
+++ options.c	23 Jun 2004 17:29:39 -0000
@@ -117,7 +117,8 @@ unsigned int backup_dir_remainder;
 
 char *backup_suffix = NULL;
 char *tmpdir = NULL;
-char *compare_dest = NULL;
+char *compare_dest[MAX_COMP_DEST+1];
+int num_comp_dest = 0;
 char *config_file = NULL;
 char *shell_cmd = NULL;
 char *log_format = NULL;
@@ -139,6 +140,7 @@ char *batch_prefix = NULL;
 
 static int daemon_opt;   /* sets am_daemon after option error-reporting */
 static int modify_window_set;
+static int saw_compare_dest = 0;
 
 /** Local address to bind.  As a character string because it's
  * interpreted by the IPv6 layer: should be a numeric IP4 or IP6
@@ -308,7 +310,7 @@ void usage(enum logcode F)
 }
 
 enum {OPT_VERSION = 1000, OPT_SENDER, OPT_EXCLUDE, OPT_EXCLUDE_FROM,
-      OPT_DELETE_AFTER, OPT_DELETE_EXCLUDED, OPT_LINK_DEST,
+      OPT_DELETE_AFTER, OPT_DELETE_EXCLUDED, OPT_COMPARE_DEST, OPT_LINK_DEST,
       OPT_INCLUDE, OPT_INCLUDE_FROM, OPT_MODIFY_WINDOW,
       OPT_READ_BATCH, OPT_WRITE_BATCH, OPT_TIMEOUT,
       OPT_REFUSED_BASE = 9000};
@@ -366,8 +368,8 @@ static struct poptOption long_options[] 
   {"max-delete",       0,  POPT_ARG_INT,    &max_delete, 0, 0, 0 },
   {"timeout",          0,  POPT_ARG_INT,    &io_timeout, OPT_TIMEOUT, 0, 0 },
   {"temp-dir",        'T', POPT_ARG_STRING, &tmpdir, 0, 0, 0 },
-  {"compare-dest",     0,  POPT_ARG_STRING, &compare_dest, 0, 0, 0 },
-  {"link-dest",        0,  POPT_ARG_STRING, &compare_dest,  OPT_LINK_DEST, 0, 0 },
+  {"compare-dest",     0,  POPT_ARG_STRING, 0,              OPT_COMPARE_DEST, 0, 0 },
+  {"link-dest",        0,  POPT_ARG_STRING, 0,              OPT_LINK_DEST, 0, 0 },
   /* TODO: Should this take an optional int giving the compression level? */
   {"compress",        'z', POPT_ARG_NONE,   &do_compression, 0, 0, 0 },
   {"daemon",           0,  POPT_ARG_NONE,   &daemon_opt, 0, 0, 0 },
@@ -585,8 +587,36 @@ int parse_arguments(int *argc, const cha
 				select_timeout = io_timeout;
 			break;
 
+		case OPT_COMPARE_DEST:
+#if HAVE_LINK
+			if (num_comp_dest >= MAX_COMP_DEST-1) {
+				rprintf(FERROR, "ERROR: %s\n", "too many --compare-dest args given");
+				return 0;
+			}
+			arg = poptGetOptArg(pc);
+			if (sanitize_paths)
+				arg = alloc_sanitize_path(arg, curr_dir);
+			compare_dest[num_comp_dest++] = (char *)arg;
+			saw_compare_dest = 1;
+			break;
+#else
+			snprintf(err_buf, sizeof err_buf,
+				 "hard links are not supported on this %s\n",
+				 am_server ? "server" : "client");
+			rprintf(FERROR, "ERROR: %s", err_buf);
+			return 0;
+#endif
+
 		case OPT_LINK_DEST:
 #if HAVE_LINK
+			if (num_comp_dest >= MAX_COMP_DEST-1) {
+				rprintf(FERROR, "ERROR: %s\n", "too many --link-dest args given");
+				return 0;
+			}
+			arg = poptGetOptArg(pc);
+			if (sanitize_paths)
+				arg = alloc_sanitize_path(arg, curr_dir);
+			compare_dest[num_comp_dest++] = (char *)arg;
 			link_dest = 1;
 			break;
 #else
@@ -661,6 +691,11 @@ int parse_arguments(int *argc, const cha
 		exit_cleanup(RERR_SYNTAX);
 	}
 
+	if (saw_compare_dest && link_dest) {
+		rprintf(FINFO,
+			"WARNING: promoting --compare-dest options to --link-dest.\n");
+	}
+
 	if (archive_mode) {
 		if (!files_from)
 			recurse = 1;
@@ -689,8 +724,6 @@ int parse_arguments(int *argc, const cha
 			(*argv)[i] = alloc_sanitize_path((*argv)[i], NULL);
 		if (tmpdir)
 			tmpdir = alloc_sanitize_path(tmpdir, curr_dir);
-		if (compare_dest)
-			compare_dest = alloc_sanitize_path(compare_dest, curr_dir);
 		if (backup_dir)
 			backup_dir = alloc_sanitize_path(backup_dir, curr_dir);
 		if (files_from)
@@ -785,8 +818,8 @@ int parse_arguments(int *argc, const cha
  **/
 void server_options(char **args,int *argc)
 {
+	static char argstr[50+MAX_COMP_DEST*2];
 	int ac = *argc;
-	static char argstr[50];
 	char *arg;
 
 	int i, x;
@@ -968,13 +1001,16 @@ void server_options(char **args,int *arg
 		args[ac++] = tmpdir;
 	}
 
-	if (compare_dest && am_sender) {
+	if (compare_dest[0] && am_sender) {
 		/* the server only needs this option if it is not the sender,
 		 *   and it may be an older version that doesn't know this
 		 *   option, so don't send it if client is the sender.
 		 */
-		args[ac++] = link_dest ? "--link-dest" : "--compare-dest";
-		args[ac++] = compare_dest;
+		int i;
+		for (i = 0; i < num_comp_dest; i++) {
+			args[ac++] = link_dest ? "--link-dest" : "--compare-dest";
+			args[ac++] = compare_dest[i];
+		}
 	}
 
 	if (files_from && (!am_sender || remote_filesfrom_file)) {
--- receiver.c	14 Jun 2004 15:09:36 -0000	1.82
+++ receiver.c	23 Jun 2004 17:29:39 -0000
@@ -36,7 +36,7 @@ extern int preserve_perms;
 extern int cvs_exclude;
 extern int io_error;
 extern char *tmpdir;
-extern char *compare_dest;
+extern char *compare_dest[];
 extern int make_backups;
 extern int do_progress;
 extern char *backup_dir;
@@ -306,7 +306,7 @@ int recv_files(int f_in,struct file_list
 	struct file_struct *file;
 	struct stats initial_stats;
 	int save_make_backups = make_backups;
-	int i, recv_ok, phase = 0;
+	int i, j, recv_ok, phase = 0;
 
 	if (verbose > 2) {
 		rprintf(FINFO,"recv_files(%d) starting\n",flist->count);
@@ -369,10 +369,10 @@ int recv_files(int f_in,struct file_list
 		/* open the file */
 		fd1 = do_open(fnamecmp, O_RDONLY, 0);
 
-		if (fd1 == -1 && compare_dest != NULL) {
+		for (j = 0; fd1 == -1 && compare_dest[j] != NULL; j++) {
 			/* try the file at compare_dest instead */
 			pathjoin(fnamecmpbuf, sizeof fnamecmpbuf,
-				 compare_dest, fname);
+				 compare_dest[j], fname);
 			fnamecmp = fnamecmpbuf;
 			fd1 = do_open(fnamecmp, O_RDONLY, 0);
 		}
--- rsync.h	16 May 2004 07:28:24 -0000	1.204
+++ rsync.h	23 Jun 2004 17:29:40 -0000
@@ -98,6 +98,8 @@
 
 #define MAX_ARGS 1000
 
+#define MAX_COMP_DEST 20
+
 #define MPLEX_BASE 7
 
 #define NO_EXCLUDES	0