Paket pack doesn't escape square brackets

Description

Nuget packages (*.nupkg) conform to the "Open Packaging Concentions", OPC. Thus files within a package are URL-adressed. This also means that reserved chars need to be percent-encoded. For most chars paket pack does the encoding correctly (e.g. a space becomes %20). Square brackets, however, get through unescaped (i.e. [] does not become %5B%5D).

This becomes an issue when processing a nuget package with .NET's OPC API (System.IO.Packaging). If a part contains a square bracket an ArgumentException is thrown, stating that the URI is not valid. And indeed, according to RFC 3986 (cf. very end of Appendix A) square brackets are reserved within a path segment and thus need to be percent-encoded.

Repro steps

1. Create a paket.template that harvests a directory
2. ensure there is a file within the harvested dir that contains square brackets (e.g. file[0].txt)
3. paket pack that template

Expected behavior

The file within the resulting nuget should look like this: file%5B0%5D.txt.

Actual behavior

The file actually looks like this: file[0].txt.

Known workarounds

None I'm aware of.

Start with the paket pack command and reproduce the issue using a harvested file named file[0].txt. Trace how harvested filenames are written into the resulting NuGet package; done means square brackets are percent-encoded as %5B and %5D, and the reproduction no longer produces an invalid OPC part URI.