JuliaLang/julia — pull request #5628 by jakebolewski (2014-01-31 05:22:01+00:00)
Title: Write a lock file when executing Pkg commands

Possible fix for https://github.com/JuliaLang/julia/issues/5622. Write a simple lock file to the package directory when executing Pkg commands to prevent multiple instances of Pkg clobbering the same directory.