Increase a testset isolation (#505)

Author: 00vareladavid

stdlib/Pkg/test/repl.jl

@@ -29,7 +29,7 @@ end
 end
 
 temp_pkg_dir() do project_path
-    cd(project_path) do
+    with_pkg_env(project_path; change_dir=true) do;
         withenv("USER" => "Test User") do
             pkg"generate HelloWorld"
             LibGit2.close((LibGit2.init(".")))

stdlib/Pkg/test/utils.jl

@@ -69,3 +69,16 @@ function with_temp_env(f, env_name::AbstractString="Dummy")
         Pkg.activate()
     end
 end
+
+function with_pkg_env(fn::Function, path::AbstractString="."; change_dir=false)
+    Pkg.activate(path)
+    try
+        if change_dir
+            cd(fn, path)
+        else
+            fn()
+        end
+    finally
+        Pkg.activate()
+    end
+end