Scripts execution context
Fisher executes all the scripts in a clean environment, to remove every chance of misbehaving on different machines. Here is described everything guaranteed about the environment.
Scripts are executed in a temporary directory created by Fisher: this allows you to download and build things without worrying about cleaning up after the execution of your script.
This directory is usually located in
/tmp, and it has a random name. It's
also set as the current working directory when the script is started, and as
$HOME. Being the home directory means most of the dotfiles and caches
created during the execution are cleared out after the build.
Fisher provides only a subset of environment variables to the processes.
System environment variables
Most of the environment variables provided by the system are removed by Fisher. A few of them are not, though: you can change them being assured all the changes will be available to the scripts.
$LANG: the system language
$PATH: the system path used to search binaries
Also, those system environment variables are overridden by Fisher:
$HOME: this is set to the build directory
$USER: this is set to the current user name
Fisher environment variables
Fisher adds its own environment variables to the mix. These variables allows you to get more information about the incoming request:
$FISHER_REQUEST_IP: the IP address of the client that sent the webhook
$FISHER_REQUEST_BODY: the path to the file containing the raw request body
Other than these variable, each provider can add its own environment variables. Check out the documentation for the providers you're using to learn more about that.