Conflicts:
	vcsh

* manpage
* set $VCSH_REPO_NAME (this assumes .git suffix!)

Conflicts:
	doc/error_codes.md

Instead of having use() report a normal error (which is actually fatal)
and returning >0, and calling use || exit $? everytime; just report the
fatal error and quit already

* move all backend code to separate functions
* call those functions directly
* simplify argument parsing
* remove redundant verbose begin/end messages

Introduce fatal(), error(), and info()

* refactor error logging code
* make all errors go to stderr
* make fatal errors actually fatal (exit instead of return)
* make output consistent

Forgot to set VCSH_COMMAND after the refactoring