Project-system: Copy and Paste references between projects

[davkean]

There's a bunch of lacking features:

• [x] ~Support copying & pasting from Solution Explorer -> File Explorer via CF_HDROP (the other way already works)~ Moved to: https://github.com/dotnet/project-system/issues/5910.
• [x] ~Support copying & pasting between Visual Studio instances. We currently use CF_VSREFPROJECTITEMS/CF_VSSTGPROJECTITEMS to copy between the same instance, but this format isn't usable in another instance because it contains the result of IVsSolution.GetProjrefOfItem which is only exchangeable in the same solution. We'd need to come up with a new format that can populate IDiskBasedDragDropItem.~
• [ ] Support copying & pasting references of all kinds; project, binary, NuGet, etc. We'd need to copy with new format to represent this, unless we can get a ref of them via IVsSolution.GetProjrefOfItem.

In CPS there's two concepts;

• IPasteDataObjectProcessor - handles paste
• ICopyPackager - handles copy

[ghuntley]

Support copying & pasting references of all kinds; project, binary, NuGet, etc.

Shutup and take my money.

[davkean]

Here's the correct way of implementing Delete-On-Paste: https://docs.microsoft.com/en-us/windows/win32/shell/datascenarios#handling-delete-on-paste-operations when communicating to Explorer/other VS instances.

[davkean]

We've moved the Solution Explorer portion of this bug to https://github.com/dotnet/project-system/issues/5910 as we'll be biting that off for 16.6.

[davkean]

Copying and pasting between Solution Explorer and Explorer has been merged. As part of that, we also enabled Copy and Paste between VS instances. This will be available in the RTM release of 16.7.

See https://twitter.com/davkean/status/1273469199810097154 for a demo of this.

Converting this bug to track just the copying and pasting of references.