core-release: Add checks to switch-to-version
core-release: Add checks to switch-to-version

Mainly adds a check to make sure the working directory is clean before
switching versions. The automatic update should not remove changes by
the user. They can do that manually if they wish.

Also restructures the function to make it a little easier to follow.

tsonntag/dotemacs,tsonntag/dotemacs,tsonntag/dotemacs,tsonntag/dotemacs