DecompressOverride #52
Description
I have been comparing the (x64 Pro) install image from Win11_24H2_English_x64.iso downloaded from Microsoft with the result of convert-UUP on 26100.1742 build (which corresponds to the build on the Microsoft ISO).
I have noticed that the Microsoft version has a smaller WinSxS folder as the convert-UUP does not utilize delta-compression on new packages/files. Upon further comparison, I have found out this is due to SOFTWARE\Microsoft\Windows\CurrentVersion\SideBySide\DecompressOverride registry entry being set to 2 in the convert-UUP image. This is due to that registry entry being present in the core professional_en-us.esd SOFTWARE registry hive - convert-UUP does not add or change it in any way. However, that registry entry is absent on the Windows image (together with \Configuration\SupersededActions, which IS being set to 3 by the script, but does not seem to do anything at all on recent Windows builds, at least not without ResetBase). When I modified convert-UPP.cmd by setting reg.exe add HKLM\%ksub%\Microsoft\Windows\CurrentVersion\SideBySide /v DecompressOverride /t REG_DWORD /d 0 /f %_Nul1% (at the same place where SupersededActions etc. are added/changed) or removing the value completely, the resulting image had all of those previously uncompressed files delta-compressed - it also had 28 additional files delta-compressed compared to the Microsoft image!
So I guess this is a bug report and/or feature request and/or food for thought regarding that registry entry: It seems Microsoft is removing it before/when they create the images to attain smaller WinSxS folder (honsetly, no idea why it is there in the esd in the first place). I also believe keeping DecompressOverride at 2 will cause future updates etc. to grow in size even more in the future on installations with that registry value (aka installations installed from images generated by convert-UUP).