Add display-message -c target-client, which causes the ‘#{client_*}’ variables to be taken from target-client.

cmd-display-message.c

@@ -115,11 +115,15 @@ cmd_display_message_exec(struct cmd *self, struct cmdq_item *item)
 
 	/*
 	 * -c is intended to be the client where the message should be
-	 * displayed if -p is not given. But it makes sense to use it for the
+	 * displayed if -p is not given, but it makes sense to use it for the
-	 * formats too, assuming it matches the session. If it doesn't, use the
+	 * client formats too. If it was given explicitly, use it even when it
-	 * best client for the session.
+	 * is not in the target session, since the formats should describe the
+	 * client which was asked for; the session, window and pane formats
+	 * still come from the target. Otherwise it is just the current client,
+	 * so only use it if it matches the session and fall back to the best
+	 * client for the session if not.
 	 */
-	if (tc != NULL && tc->session == s)
+	if (tc != NULL && (args_has(args, 'c') || tc->session == s))
 		c = tc;
 	else if (s != NULL)
 		c = cmd_find_best_client(s);

tmux.1

@@ -8328,11 +8328,17 @@ Otherwise, the format of
 .Ar message
 is described in the
 .Sx FORMATS
-section; information is taken from
+section; session, window and pane information is taken from
 .Ar target\-pane
 if
 .Fl t
 is given, otherwise the active pane.
+If
+.Fl c
+is given, the
+.Ql #{client_*}
+variables are taken from
+.Ar target\-client .
 .Pp
 If
 .Fl j