Pyro needs to be able to build patches even if some .wixmsts contain no changes

[wixbot]

Currently, I may have a patch that targets multiple Components A, B, and C and multiple Products Y and Z. It may be that Product MSI Z contains Components A and C while Product MSI Y contains Components B and C.

My Product may also have various baselines such as RTM and Service Pack 1. The current Pyro design makes it difficult to build such a patch. If a Binary in Component B changes, the patch should correctly update Product MSI Y but it will not because the .wixmst for Product MSI Z contains no changes.

This requires a huge amount of maintenance to continually update the patch definitions and know when Components have changes.

The feature request here is to allow Pyro, with a command-line parameter, to ignore the empty transform for Product Z in this case and simply patch Product Y. Later, when other changes are made to the Products, the patch will be able to pick them up and target both Product MSI Z and Y.

Originally opened by samuels

[wixbot]

A WiP for this change is now at https://github.com/wixtoolset/site/blob/master/root/src/documents/development/wips/4385-allow-pyro-to-ignore-empty-wixmsts-and-still-build-a-patch.html.md.

Originally posted by samuels