Q:

julia - How can I fix unkown package error?

I have faced an error many times when installing packages to Julia.
I googled the solution and tried many solutions, but non of them solved my problem including removing the .julia folder in my documents.
This is when I try to install Splines:
Pkg.add("Splines")

The error says:
ERROR: unknown package Splines
macro expansion at .\pkg\entry.jl:53 [inlined]
(::Base.Pkg.Entry.##1#3{String,Base.Pkg.Types.VersionSet})() at .\task.jl:335
Stacktrace:
 [1] sync_end() at .\task.jl:287
 [2] macro expansion at .\task.jl:303 [inlined]
 [3] add(::String, ::Base.Pkg.Types.VersionSet) at .\pkg\entry.jl:51
 [4] (::Base.Pkg.Dir.##4#7{Array{Any,1},Base.Pkg.Entry.#add,Tuple{String}})() at .\pkg\dir.jl:36
 [5] cd(::Base.Pkg.Dir.##4#7{Array{Any,1},Base.Pkg.Entry.#add,Tuple{String}}, ::String) at .\file.jl:59
 [6] #cd#1(::Array{Any,1}, ::Function, ::Function, ::String, ::Vararg{String,N} where N) at .\pkg\dir.jl:36
 [7] add(::String) at .\pkg\pkg.jl:117

A:

Splines.jl is not a registered package.
Try:
Pkg.checkout("git@github.com:bnels/Splines.jl.git"); Pkg.build("Splines")

