"The command line is too long." on git.add()

[cloewen8]

The Issue

When adding a large number of files (143), git.add will fail. I believe this would also happen with long path names as well.

As a temporary workaround, I will create a custom stream to flush a limited number of files at once.

A Solution (maybe)

I haven't worked with Streams for a while, so please disregard this if I am incorrect.
In Node.js 1.2.0, they added a simplified way to construct writable streams (https://nodejs.org/api/stream.html#stream_simplified_construction). If this was used instead of through2, writev could be implemented. writev is designed to write multiple chunks at once and would be better suited for the task. The amount written using pipe can be customized by setting highWaterMark (untested).

Assuming this is a viable solution, I would be happy to implement it and any applicable tests.

[stephenlacy]

PR would be accepted, thanks