doc: mention how to turn on pure evaluation mode in manual

The flag is `--pure-eval`, which can be found by looking at the test suite; it
should be in the notes describing the feature as well, since otherwise users may
assume this is referencing something like `nix-shell --pure`.
This commit is contained in:
Benjamin Hipple 2020-02-15 01:37:44 -05:00
parent 9af10b753c
commit 762febafe2

View file

@ -503,14 +503,14 @@
</listitem>
<listitem>
<para><emphasis>Pure evaluation mode</emphasis>. This is a variant
of the existing restricted evaluation mode. In pure mode, the Nix
evaluator forbids access to anything that could cause different
evaluations of the same command line arguments to produce a
<para><emphasis>Pure evaluation mode</emphasis>. With the
<literal>--pure-eval</literal> flag, nix enables a variant of the existing
restricted evaluation mode that forbids access to anything that could cause
different evaluations of the same command line arguments to produce a
different result. This includes builtin functions such as
<function>builtins.getEnv</function>, but more importantly,
<emphasis>all</emphasis> filesystem or network access unless a
content hash or commit hash is specified. For example, calls to
<emphasis>all</emphasis> filesystem or network access unless a content hash
or commit hash is specified. For example, calls to
<function>builtins.fetchGit</function> are only allowed if a
<varname>rev</varname> attribute is specified.</para>