git dependencies don't work with relative paths

Description

Using a `:git/url` of "." or ".." doesn't work, and results in a stacktrace. I suspect this is due to the naming of the output directory being dependent in the input path. In this case, I would expect the artifact name to factor into the name of the repository OR to mirror the absolute path as nested within the `.gitlibs` directory:

`.gitlibs/_repos/home/dominic/myproject`

Environment

None

Assignee

Alex Miller

Reporter

Dominic Monroe

Labels

None

Approval

None

Patch

None

Priority

Minor
Configure