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 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.