Terminate copy iteration when hitting in-place nimbleDir (#429)

* terminate copy iteration when hitting in-place nimbleDir; fixes #428

* investigate travis issue

* more investigations

* more investigations

* fix nim version issue

tests/issue428/dummy.nimble

@@ -0,0 +1,10 @@
+# Package
+
+version       = "0.1.0"
+author        = "Author"
+description   = "dummy"
+license       = "MIT"
+
+# Dependencies
+
+requires "nim >= 0.17.0"

tests/tester.nim

@@ -354,6 +354,13 @@ test "issue #338":
   cd "issue338":
     check execNimble("install", "-y").exitCode == QuitSuccess
 
+test "issue #428":
+  cd "issue428":
+    # Note: Can't use execNimble because it patches nimbleDir
+    check execCmdEx(nimblePath & " -y --nimbleDir=./nimbleDir install").exitCode == QuitSuccess
+    check dirExists("nimbleDir/pkgs/dummy-0.1.0")
+    check(not dirExists("nimbleDir/pkgs/dummy-0.1.0/nimbleDir"))
+
 test "can list":
   check execNimble("list").exitCode == QuitSuccess