Is there any way to build package dependency tree in julia-lang?

I don't think there's a simple function, but it shouldn't be too hard to do with these two functions:

julia> Pkg.dependents("Cairo")
10-element Array{AbstractString,1}:
 "Tk"
 "Gtk"
 "Mamba"
 "Drawing"
 "GtkUtilities"
 "ProfileView"
 "Brim"
 "Winston"
 "EcologicalNetwork"
 "VennEuler"

julia> Pkg.installed()
Dict{ASCIIString,VersionNumber} with 119 entries:
  "Libz"             => v"0.0.2"
  "Gtk"              => v"0.9.3"
  "Interact"         => v"0.3.0"
  "ForwardDiff"      => v"0.1.4"
  "Benchmark"        => v"0.1.0"
  "AxisAlgorithms"   => v"0.1.4"
  "Cairo"            => v"0.2.31+"
  "HttpParser"       => v"0.1.1"
  "DataFrames"       => v"0.6.10"
  "Requests"         => v"0.3.4"
  "QuartzImageIO"    => v"0.1.0+"
  "Markdown"         => v"0.3.0"
  "Requires"         => v"0.2.2"
  "ArgParse"         => v"0.3.0"
  ⋮                  => ⋮

simple code bellow will printout the requires-by result for a package:

whorequires(pkgname) = whorequires(pkgname, 0);
function whorequires(pkgname, i)
  deps = Pkg.dependents(pkgname);
  [print('-') for j=1:i];
  println(pkgname);
  length(deps) > 0 && [whorequires(dep,i+1) for dep in deps];
end

julia> whorequires("JuliaParser");
JuliaParser
-CodeTools
--Atom
-ASTInterpreter
--Gallium
-Jewel

EDIT (to cover issue commented by @amrods)

whorequires(pkgname) = whorequires(pkgname, 0, Dict{ASCIIString,Vector{ASCIIString}}());
function whorequires(pkgname, i, m)
  [print('-') for j=1:i];
  if (haskey(m,pkgname))
    println("$pkgname *[duplicated]* is required by ", length(m[pkgname]), " packages");
  else
    println(pkgname);
    m[pkgname] = Pkg.dependents(pkgname);
    if (length(m[pkgname]) > 0)
        for dep in m[pkgname]
            whorequires(dep,i+1,m);
        end
    end
  end
end