Make versioned .julia/v0.x dir by default.

base/pkg/cache.jl

@@ -3,10 +3,35 @@ module Cache
 import ..Git
 using ..Types
 
-path(pkg::String) = abspath(".cache", pkg)
+import ..Dir: pkgroot, path
+
+function mkcachedir()
+    cache = realpath(abspath(".cache"))
+    if isdir(cache)
+        return
+    end
+
+    @windows_only mkdir(cache)
+    @unix_only begin
+        rootcache = realpath(joinpath(pkgroot(), ".cache"))
+        if rootcache == cache
+            mkdir(cache)
+        elseif isdir(rootcache)
+            try
+                ln(rootcache, cache)
+            catch
+                mkdir(cache)
+            end
+        else
+            mkdir(rootcache)
+            mkcachedir()
+        end
+    end
+end
+
 
 function prefetch{S<:String}(pkg::String, url::String, sha1s::Vector{S})
-    isdir(".cache") || mkdir(".cache")
+    isdir(".cache") || mkcachedir()
     cache = path(pkg)
     if !isdir(cache)
         info("Cloning cache of $pkg from $url")

base/pkg/dir.jl

@@ -5,13 +5,15 @@ import ..Git
 
 const DIR_NAME = ".julia"
 
+pkgroot() = abspath(get(ENV,"JULIA_PKGDIR",joinpath(homedir(),DIR_NAME)))
+
 function path()
-    b = abspath(get(ENV,"JULIA_PKGDIR",joinpath(homedir(),DIR_NAME)))
+    b = pkgroot()
     x, y = VERSION.major, VERSION.minor
     d = joinpath(b,"v$x.$y")
-    isdir(d) && return d
-    d = joinpath(b,"v$x")
-    isdir(d) && return d
+    if isdir(d) || !isdir(b) || !isdir(joinpath(b, "METADATA"))
+        return d
+    end
     return b
 end
 path(pkg::String...) = normpath(path(),pkg...)