river: add send-to-previous-tags command

river/command.zig

@@ -83,6 +83,7 @@ const str_to_impl_fn = [_]struct {
     .{ .name = "toggle-fullscreen",      .impl = @import("command/toggle_fullscreen.zig").toggleFullscreen },
     .{ .name = "toggle-view-tags",       .impl = @import("command/tags.zig").toggleViewTags },
     .{ .name = "focus-previous-tags",    .impl = @import("command/tags.zig").focusPreviousTags },
+    .{ .name = "send-to-previous-tags",  .impl = @import("command/tags.zig").sendToPreviousTags },
     .{ .name = "unmap",                  .impl = @import("command/map.zig").unmap },
     .{ .name = "unmap-pointer",          .impl = @import("command/map.zig").unmapPointer },
     .{ .name = "xcursor-theme",          .impl = @import("command/xcursor_theme.zig").xcursorTheme },

river/command/tags.zig

@@ -121,6 +121,22 @@ pub fn focusPreviousTags(
     }
 }
 
+/// Set the tags of the focused view to the tags that were selected previously
+pub fn sendToPreviousTags(
+    allocator: *std.mem.Allocator,
+    seat: *Seat,
+    args: []const []const u8,
+    out: *?[]const u8,
+) Error!void {
+    const previous_tags = seat.focused_output.previous_tags;
+    if (seat.focused == .view) {
+        const view = seat.focused.view;
+        view.pending.tags = previous_tags;
+        seat.focus(null);
+        view.applyPending();
+    }
+}
+
 fn parseTags(
     allocator: *std.mem.Allocator,
     args: []const [:0]const u8,