docs: be more precise on what `spack add ...` does (#23204)

This is as much a question as it is a minor fine-tuning of the docs.  I've been known to add things to an environment by editing the `spack.yaml` file directly.  When I read the previous version of this sentence, I was afraid that `spack add` was actually doing *two* things, modifying the `spack.yaml` and updating something else that defined the roots of the Environment.  A bit of experimentation suggests that editing the `spack.yaml` file is sufficient to change the roots.

Co-authored-by: Adam J. Stewart <ajstewart426@gmail.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/lib/spack/docs/environments.rst b/lib/spack/docs/environments.rst
index 1a52ac8328..76b974ff62 100644
--- a/lib/spack/docs/environments.rst
+++ b/lib/spack/docs/environments.rst
@@ -248,9 +248,9 @@ Users can add abstract specs to an Environment using the ``spack add``
 command. The most important component of an Environment is a list of
 abstract specs.
 
-Adding a spec adds to the manifest (the ``spack.yaml`` file) and to
-the roots of the Environment, but does not affect the concrete specs
-in the lockfile, nor does it install the spec.
+Adding a spec adds to the manifest (the ``spack.yaml`` file), which is
+used to define the roots of the Environment, but does not affect the
+concrete specs in the lockfile, nor does it install the spec.
 
 The ``spack add`` command is environment aware. It adds to the
 currently active environment. All environment aware commands can also