diff --git a/man/mu-mv.1 b/man/mu-mv.1
index b6000209..a64161d7 100644
--- a/man/mu-mv.1
+++ b/man/mu-mv.1
@@ -46,10 +46,20 @@ The flags is a sequence of characters from the set D (draft), F (flagged), N
 flags-parameter is case-sensitive. Any other characters will be silently
 ignored.
 
+The \fB\-\-flags\fR also has a second, 'delta', syntax. In this syntax, each
+of the flag characters is prefixed with either '+' or '-', which means that
+the corresponding flag will be added or removed. Using this syntax, you can
+change individual flags, without changing all of them.
+
 .TP
-\fB\-\-printtarget\fR
+\fB\-\-print-target\fR
 return the target path on standard output upon succesful completion of the
-move (with or without a succesful database update)
+move (with or without a succesful database update).
+
+.TP
+\fB\-\-ignore-dups\fR
+silently ignore the case where the source file is the same as the target.
+
 
 .SH EXAMPLE
 
@@ -76,23 +86,30 @@ To mark a message as no longer new and 'Seen', and update the database
 afterwards, you could do:
 
 .nf
-   mu --flags=S mv /home/roger/Maildir/inbox/new/123123123 /home/roger/Maildir/inbox/
+   mu mv /home/roger/Maildir/inbox/new/123123123 /home/roger/Maildir/inbox/ --flags=S
 .fi
 
 In this case, as we are not moving the message to a diffent maildir, we can
 leave off the maildir-argument; so the following is equivalent:
 
 .nf
-   mu --flags=S mv /home/roger/Maildir/inbox/new/123123123 
+   mu mv /home/roger/Maildir/inbox/new/123123123  --flags=S
 .fi
 
+Finally, using the 'delta'-syntax, you can set the 'seen'-flag
+and 'replied'-flag while removing the 'new' flag with:
+
+.nf
+   mu mv /home/billy/Maildir/inbox/new/12aa34343 --flags=+S+R-N 
+.fi
+which would give us a new file:
+\fI/home/billy/Maildir/inbox/cur/12aa34343:2,SR\fR
 
 .SH LIMITATIONS
 
 Both source-path and target-directory must be on the same disk partition,
 except when the target-directory is \fI/dev/null\fR.
 
-
 .SH RETURN VALUE
 
 \fBmu mv\fR returns 0 upon success, and some other value when an error
diff --git a/src/mu-cmd.c b/src/mu-cmd.c
index dd38cab2..12e295fb 100644
--- a/src/mu-cmd.c
+++ b/src/mu-cmd.c
@@ -285,19 +285,31 @@ mu_cmd_mkdir (MuConfig *opts)
 static gboolean
 mv_check_params (MuConfig *opts, MuFlags *flags)
 {
-	if (!opts->params[1] || !opts->params[2]) {
+	if (!opts->params[1]) {
 		g_warning ("usage: mu mv [--flags=<flags>] <mailfile> "
-			   "<maildir>");
+			   "[<maildir>]");
 		return FALSE;
 	}
 
 	/* FIXME: check for invalid flags */
 	if (!opts->flagstr)
 		*flags = MU_FLAG_INVALID; /* ie., ignore flags */
-	else
-		*flags = mu_flags_from_str (opts->flagstr,
-					    MU_FLAG_TYPE_MAILDIR |
-					    MU_FLAG_TYPE_MAILFILE);
+	else {
+		/* if there's a '+' or '-' sign in the string, it must
+		 * be a flag-delta */
+		if (strstr (opts->flagstr, "+") || strstr (opts->flagstr, "-")) {
+			MuFlags oldflags;
+			oldflags = mu_maildir_get_flags_from_path (opts->params[1]);
+			*flags = mu_flags_from_str_delta (opts->flagstr,
+							  oldflags,
+							  MU_FLAG_TYPE_MAILDIR|
+							  MU_FLAG_TYPE_MAILFILE);
+		} else
+			*flags = mu_flags_from_str (opts->flagstr,
+						    MU_FLAG_TYPE_MAILDIR |
+						    MU_FLAG_TYPE_MAILFILE);
+	}
+	
 	return TRUE;
 }
 
@@ -310,7 +322,7 @@ cmd_mv_dev_null (MuConfig *opts)
 		return MU_ERROR_FILE;
 	}
 	
-	if (opts->printtarget)
+	if (opts->print_target)
 		g_print ("/dev/null\n"); /* /dev/null */
 
 	return MU_OK;
@@ -334,7 +346,8 @@ mu_cmd_mv (MuConfig *opts)
 	err = NULL;
 	fullpath = mu_maildir_move_message (opts->params[1],
 					    opts->params[2],
-					    flags, &err);
+					    flags, opts->ignore_dups,
+					    &err);
 	if (!fullpath) {
 		if (err) {
 			MuError code;
@@ -346,7 +359,7 @@ mu_cmd_mv (MuConfig *opts)
 		return MU_ERROR_FILE;
 		
 	} else {
-		if (opts->printtarget)       
+		if (opts->print_target)       
 			g_print ("%s\n", fullpath); 
 		return MU_OK;
 	}
diff --git a/src/mu-config.c b/src/mu-config.c
index 0436c3c6..d62d9f95 100644
--- a/src/mu-config.c
+++ b/src/mu-config.c
@@ -322,7 +322,10 @@ config_options_group_mv (MuConfig *opts)
 	GOptionEntry entries[] = {
 		{"flags", 0, 0, G_OPTION_ARG_STRING, &opts->flagstr,
 		 "flags to set for the target (DFNPRST)", NULL},
-		{"printtarget", 0, 0, G_OPTION_ARG_NONE, &opts->printtarget,
+		{"ignore-dups", 0, 0, G_OPTION_ARG_NONE, &opts->ignore_dups,
+		 "whether to silently ignore the source = target case",
+		 NULL},
+		{"print-target", 0, 0, G_OPTION_ARG_NONE, &opts->print_target,
 		 "whether to print the target path upon succesful completion",
 		 NULL},
 		{NULL, 0, 0, 0, NULL, NULL, NULL}
diff --git a/src/mu-config.h b/src/mu-config.h
index 0cebf13a..0837ab02 100644
--- a/src/mu-config.h
+++ b/src/mu-config.h
@@ -128,10 +128,11 @@ struct _MuConfig {
 	/* options for mv */
 	char            *flagstr;        /* message flags to set for
 					  * the target */
-	gboolean	printtarget;      /* should be print the
-					   * target file path on
-					   * stdout */
-	
+	gboolean	print_target;    /* should be print the
+					  * target file path on
+					  * stdout */
+	gboolean        ignore_dups;      /* silently ignore the
+					   * src=target case */
 	/* options for view */
 	gboolean         terminator;      /* add separator \f between
 					   * multiple messages in mu
diff --git a/src/mu-flags.c b/src/mu-flags.c
index 2ea79a17..d8286346 100644
--- a/src/mu-flags.c
+++ b/src/mu-flags.c
@@ -60,7 +60,6 @@ mu_flag_type (MuFlags flag)
 	if (flag >= MU_FLAG_SIGNED && flag <= MU_FLAG_HAS_ATTACH)
 		return MU_FLAG_TYPE_CONTENT;
 
-	g_return_val_if_reached (MU_FLAG_TYPE_INVALID);
 	return MU_FLAG_TYPE_INVALID;
 }
 
@@ -87,7 +86,6 @@ mu_flag_char (MuFlags flag)
 	case MU_FLAG_UNREAD:		return	'u';
 
 	default:
-		g_return_val_if_reached (0);
 		return 0;
 	}
 }
@@ -115,13 +113,11 @@ mu_flag_from_char (char kar)
 	case 'u': return MU_FLAG_UNREAD;	
 		
 	default:
-		g_return_val_if_reached (MU_FLAG_INVALID);
 		return MU_FLAG_INVALID;
 	}
 }
 
 
-
 /* does not use FLAG_INFO, optimized */
 const char*
 mu_flag_name (MuFlags flag)
@@ -143,7 +139,6 @@ mu_flag_name (MuFlags flag)
 	case MU_FLAG_UNREAD:		return  "unread";	
 		
 	default:
-		g_return_val_if_reached (NULL);
 		return NULL;
 	}
 }
@@ -160,7 +155,7 @@ mu_flags_to_str_s (MuFlags flags, MuFlagType types)
 		    types & FLAG_INFO[u].flag_type)
 			str[v++] = FLAG_INFO[u].kar;
 	str[v] = '\0';
-
+	
 	return str;
 }
 
@@ -199,3 +194,39 @@ mu_flags_foreach (MuFlagsForeachFunc func, gpointer user_data)
 		func (FLAG_INFO[u].flag, user_data);
 }
 
+
+MuFlags
+mu_flags_from_str_delta (const char *str, MuFlags oldflags,
+			 MuFlagType types)
+{
+	const char *cur;
+	MuFlags newflags;
+		
+	g_return_val_if_fail (str, MU_FLAG_INVALID);
+
+	for (cur = str, newflags = oldflags; *cur; ++cur) {
+
+		MuFlags f;
+		if (*cur == '+' || *cur == '-') {
+			f = mu_flag_from_char (cur[1]);
+			if (f == 0)
+				goto error;
+			if (*cur == '+')
+				newflags  |= f;
+			else
+				newflags  &= ~f;
+			++cur;		
+			continue;
+		}
+
+		goto error;
+	}
+	
+	return newflags;
+error:
+	g_warning ("invalid flag string");
+	return MU_FLAG_INVALID;
+	
+}
+
+
diff --git a/src/mu-flags.h b/src/mu-flags.h
index 1f5681b7..002285b7 100644
--- a/src/mu-flags.h
+++ b/src/mu-flags.h
@@ -122,6 +122,26 @@ const char* mu_flags_to_str_s (MuFlags flags, MuFlagType types);
 MuFlags mu_flags_from_str (const char *str, MuFlagType types);
 
 
+
+/**
+ * Update #oldflags with the flags in #str, where #str consists of the
+ * the normal flag characters, but prefixed with either '+' or '-',
+ * which means resp. "add this flag" or "remove this flag" from
+ * oldflags.  So, e.g. "-N+S" would unset the NEW flag and set the
+ * SEEN flag, without affecting other flags.
+ * 
+ * @param str the string representation
+ * @param old flags to update
+ * @param types the flag types to accept (other will be ignored)
+ * 
+ * @return 
+ */
+MuFlags mu_flags_from_str_delta (const char *str, MuFlags oldflags,
+				 MuFlagType types);
+
+
+
+
 typedef void (*MuFlagsForeachFunc) (MuFlags flag, gpointer user_data);
 
 /**
diff --git a/src/mu-maildir.c b/src/mu-maildir.c
index cce2e21e..7374494b 100644
--- a/src/mu-maildir.c
+++ b/src/mu-maildir.c
@@ -812,10 +812,12 @@ msg_move (const char* src, const char *dst, GError **err)
 
 gchar*
 mu_maildir_move_message (const char* oldpath, const char* targetmdir,
-			 MuFlags newflags, GError **err)
+			 MuFlags newflags, gboolean ignore_dups,
+			 GError **err)
 {
 	char *newfullpath;
 	gboolean rv;
+	gboolean src_is_target;
 	
 	g_return_val_if_fail (oldpath, FALSE);
 	
@@ -827,16 +829,21 @@ mu_maildir_move_message (const char* oldpath, const char* targetmdir,
 		return FALSE;
 	}
 
-	if (g_strcmp0 (oldpath, newfullpath) == 0) {
+
+	src_is_target = (g_strcmp0 (oldpath, newfullpath) == 0);
+	
+	if (!ignore_dups && src_is_target) {
 		g_set_error (err, 0, MU_ERROR_FILE_TARGET_EQUALS_SOURCE,
 			     "target equals source");
 		return FALSE;
 	}
 
-	rv = msg_move (oldpath, newfullpath, err);
-	if (!rv) {
-		g_free (newfullpath);
-		return NULL;
+	if (!src_is_target) {
+		rv = msg_move (oldpath, newfullpath, err);
+		if (!rv) {
+			g_free (newfullpath);
+			return NULL;
+		}
 	}
 	
 	return newfullpath;
diff --git a/src/mu-maildir.h b/src/mu-maildir.h
index abf2f90a..1a7c9e19 100644
--- a/src/mu-maildir.h
+++ b/src/mu-maildir.h
@@ -171,14 +171,17 @@ char* mu_maildir_get_new_path (const char *oldpath, const char *new_mdir,
  * of the message are affected; note that this may still involve a
  * moved to another directory (say, from new/ to cur/)
  * @param flags to set for the target (influences the filename, path)
+ * @param ignore_dups whether to silent ignore the src=target case (and return TRUE)
  * @param err (may be NULL) may contain error information; note if the
  * function return FALSE, err is not set for all error condition
  * (ie. not for parameter errors)
+ * 
  * @return return the full path name of the target file (g_free) if
  * the move succeeded, NULL otherwise
  */
 gchar* mu_maildir_move_message (const char* oldpath, const char* targetmdir,
-				MuFlags newflags, GError **err);
+				MuFlags newflags, gboolean ignore_dups,
+				GError **err);
 
 G_END_DECLS