Setting the error option in bash bypasses error handling in the forgit
functions, because the script immediatley exits in case of an error.
Remove the option to make error handling possible.
Bash scripts automatically return the exit code of the last statement,
so standalone forgit will still return useful error codes.
From the standalone forgit command we call the according forgit function
by replacing a '_' with '::'. Since we have more complex function names
like 'forgit::cherry:⛏️:from::branch' we have to replace ALL
instances of '_' instead of just the first one.
Using an underscore instead of a dash simplifies the workflow and
documentation by making the commands and environment variables that
forgit uses the same (i.e. `git forgit checkout_file` is the same
command referred to by `forgit_checkout_file`)
