Author: Jan Christoph Ebersbach <jceb@e-jc.de>
URL: http://dwm.suckless.org/patches/historical/tagall
Shortcut to move all (floating) windows from one tag to another.

Index: dwm/tagall.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ dwm/tagall.c	2014-02-09 15:24:11.468116949 +0100
@@ -0,0 +1,24 @@
+void
+tagall(const Arg *arg) {
+	if (!selmon->clients)
+		return;
+	/* if parameter starts with F, just move floating windows */
+	int floating_only = (char *)arg->v && ((char *)arg->v)[0] == 'F' ? 1 : 0;
+	int tag = (char *)arg->v ? atoi(((char *)arg->v) + floating_only) : 0;
+	int j;
+	Client* c;
+	if(tag >= 0 && tag < LENGTH(tags))
+		for(c = selmon->clients; c; c = c->next)
+		{
+			if(!floating_only || c->isfloating)
+				for(j = 0; j < LENGTH(tags); j++)
+				{
+					if(c->tags & 1 << j && selmon->tagset[selmon->seltags] & 1 << j)
+					{
+						c->tags = c->tags ^ (1 << j & TAGMASK);
+						c->tags = c->tags | 1 << (tag-1);
+					}
+				}
+		}
+	arrange(selmon);
+}