using and include changes

[StefanKarpinski]

See #9079 and #4600. The first half should be done for 0.4:

• make using and import look in current directory only when in REPL or top-level script
• while loading other code, only look in Pkg.dir() and LOAD_PATH

The second half should be explored in the next release cycle:

• implement relative using/import should search current directory #4600 to allow relative using and import

[kmsquire]

I know this is trying to solve #9079, but I don't love the idea of things running differently between the command line and the REPL.

[tkelman]

We lived fine with the behavior prior to #9079, and changing it caused way more issues than it fixed. I think avoiding loading from the current directory would be fine for now.

[StefanKarpinski]

I would be ok with not looking in the current directory even in the REPL or top-level of a script. With #4600 one would be able to write using .Foo to load Foo.jl from the current directory in the REPL.

[nalimilan]

+1 to not looking in the current directory and not introducing a different behaviour at the REPL.

[JeffBezanson]

Fine with me.

[aviks]

include continues to be relative to the file, right?

Happy with this, thanks!

[JeffBezanson]

include continues to be relative to the file, right?

Correct.