undocumented flag -J to skip committing the new sync state.

src/isync.h

@@ -196,6 +196,7 @@ extern const char *Home;
 #define VERBOSE      2
 #define QUIET        4
 #define VERYQUIET    8
+#define KEEPJOURNAL  16
 
 extern int DFlags;
 

src/main.c

@@ -372,6 +372,9 @@ main( int argc, char **argv )
 		case 'D':
 			DFlags |= DEBUG | QUIET;
 			break;
+		case 'J':
+			DFlags |= KEEPJOURNAL;
+			break;
 		case 'v':
 			version();
 		case 'h':

src/sync.c

@@ -914,9 +914,11 @@ sync_boxes( store_t *ctx[], const char *names[], channel_conf_t *chan )
 
 	fclose( nfp );
 	fclose( jfp );
+	if (!(DFlags & KEEPJOURNAL)) {
 		/* order is important! */
 		rename( nname, dname );
 		unlink( jname );
+	}
 
   bail:
 	for (srec = recs; srec; srec = nsrec) {