Environment variables

Everything in the environment that changes what niwa does. Nothing else in it is read.

What niwa reads

A path variable is honored only when it is absolute. Anything else is ignored, and the default stands.

Variable	What it does
`HOME`	The home directory. It must be set and absolute, or niwa stops before it does anything.
`XDG_CONFIG_HOME`	Moves the config repo to <value>/niwa. Honored when absolute, ignored otherwise.
`XDG_STATE_HOME`	Moves the state directory to <value>/niwa. Honored when absolute, ignored otherwise.
`XDG_DATA_HOME`	Moves shared data, including the shipped types and resolved modules. Honored when absolute.
`HOMEBREW_PREFIX`	Where Homebrew lives, in place of the architecture default. Honored when absolute.
`NIWA_MANAGED_PREFS`	Where managed preferences are read from. It exists so the tests can run against a fake one.
`NIWA_PROGRESS_EVERY`	How often a long run prints a progress line, in seconds. The default is 30.
`NO_COLOR`	Set and not empty: no color. The marks stay, so the screen still reads.
`FORCE_COLOR`	Set, not empty, and not "0": color even when the output is a pipe.
`TERM`	"dumb" turns color off, like NO_COLOR.
`TERM_PROGRAM`	Names the terminal. On the ones known to render OSC 8, niwa prints clickable links.
`EDITOR`	The editor pull opens for the edit answer. It may carry arguments, for example "code --wait".
`ZDOTDIR`	Where .zshrc lives. uninstall reads it to find the PATH line the installer wrote.
`PATH`	Where niwa finds the tools it drives, and what every command it runs inherits.

install.sh reads two more. They are for mirrors and for testing; neither is needed to install niwa.

Variable	What it does
`NIWA_RELEASE_BASE`	Where install.sh fetches a release from. For mirrors, and for testing.
`NIWA_VERSION`	The version install.sh fetches. The default is the current release.

File locations — say where every file lives and which are committed
Reference — index the twenty verbs by how often you reach for them, and route to the rest