Currently, the `vcs` subcommand does not export environment variables in the same way that the `commit` subcommand does.  It can be useful to have those environment variables in some cases, though, such as when you're using git and wanting to run a `revert` subcommand (e.g. with `$ sudo etckeeper vcs revert $REVISION`), as the `revert` functionality includes committing the reverted change.

I submit [this pull request](https://github.com/Juanc1to/etckeeper/tree/vcs_export) as a possible strategy to implement this: it currently duplicates the environment export logic from the `commit` subcommand.  It might make sense to refactor this out into some sort of library, but I'm not really familiar enough with shell script project conventions (or the maintainer's style goals) to suggest a strategy for this.
