Can you remove the Color Space node changes as you already have submitted D12481: Compositing Convert color space node.

Could you also update this patch the reflect the changes in master?

Notible changes, node_composite_3dLut.c needs to be migrated to c++.
There is a new API for declaring node sockets, see examples of NodeDeclarationBuilder

Thanks for working on this, I think these nodes can be very useful.
There has been style changes in compositor (mostly naming convention), I've updated the diff to reflect the changes because it's my fault, sorry for the hassle.
Please continue from this diff:

• Can you split it in two patches as before, please? One per node. Patches should have only one feature.

I assume this patch is for the 3dLut node:

• Please explain briefly in the description what is a Lut and what the node can be used for. It's for users and the commit message.
• I get this warning:

bf/blender/source/blender/compositor/operations/COM_Color3dLutOperation.cc:72:5: warning: do not use 'else' after 'continue' [readability-else-after-return]
    else if (sscanf(line, "TITLE%*[ \t]%[^\n]", title) == 1) {
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Will comment further once the patch is updated.

Note: You can manage patches with arcanist -> https://wiki.blender.org/wiki/Tools/CodeReview#Use_Arcanist

Patch needs to be updated with master.