Respect workspace numbers when looking for a free workspace name

This prevents a ws '1' appearing on a new output when there's
already a ws '1: www' on an existing output

src/workspace.c

@@ -197,17 +197,16 @@ Con *create_workspace_on_output(Output *output, Con *content) {
         while (exists) {
             c++;
 
-            FREE(ws->name);
-            sasprintf(&(ws->name), "%d", c);
+            ws->num = c;
 
             current = NULL;
             TAILQ_FOREACH(out, &(croot->nodes_head), nodes)
-                GREP_FIRST(current, output_get_content(out), !strcasecmp(child->name, ws->name));
+                GREP_FIRST(current, output_get_content(out), child->num == ws->num);
             exists = (current != NULL);
 
-            DLOG("result for ws %s / %d: exists = %d\n", ws->name, c, exists);
+            DLOG("result for ws %d: exists = %d\n", c, exists);
         }
-        ws->num = c;
+        sasprintf(&(ws->name), "%d", c);
     }
     con_attach(ws, content, false);
 

testcases/t/515-create-workspace.t

@@ -0,0 +1,40 @@
+#!perl
+# vim:ts=4:sw=4:expandtab
+#
+# Please read the following documents before working on tests:
+# • http://build.i3wm.org/docs/testsuite.html
+#   (or docs/testsuite)
+#
+# • http://build.i3wm.org/docs/lib-i3test.html
+#   (alternatively: perldoc ./testcases/lib/i3test.pm)
+#
+# • http://build.i3wm.org/docs/ipc.html
+#   (or docs/ipc)
+#
+# • http://onyxneon.com/books/modern_perl/modern_perl_a4.pdf
+#   (unless you are already familiar with Perl)
+#
+# Tests that new workspace names are taken from the config,
+# then from the first free number starting with 1.
+#
+use i3test i3_autostart => 0;
+
+my $config = <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+fake-outputs 1024x768+0+0,1024x768+1024+0
+
+bindsym 1 workspace 1: eggs
+EOT
+my $pid = launch_with_config($config);
+
+my $i3 = i3(get_socket_path());
+my $ws = $i3->get_workspaces->recv;
+
+is($ws->[0]->{name}, '1: eggs', 'new workspace uses config name');
+is($ws->[1]->{name}, '2', 'naming continues with next free number');
+
+exit_gracefully($pid);
+
+done_testing;