Do not initialize config on spack compiler list (#28042)

When `spack compiler list` is run without being restricted to a
particular scope, and no compilers are found, say that none are 
available, and hint that the use should run spack compiler find to 
auto detect compilers.

* Improve docs
* Check if stdin is a tty
* add a test

1 files changed, 9 insertions, 7 deletions

diff --git a/lib/spack/docs/getting_started.rst b/lib/spack/docs/getting_started.rst
index aa56890847..f0ee86eb72 100644
--- a/lib/spack/docs/getting_started.rst
+++ b/lib/spack/docs/getting_started.rst
@@ -271,9 +271,10 @@ Compiler configuration
 ----------------------
 
 Spack has the ability to build packages with multiple compilers and
-compiler versions. Spack searches for compilers on your machine
-automatically the first time it is run. It does this by inspecting
-your ``PATH``.
+compiler versions. Compilers can be made available to Spack by
+specifying them manually in ``compilers.yaml``, or automatically by
+running ``spack compiler find``, but for convenience Spack will
+automatically detect compilers the first time it needs them.
 
 .. _cmd-spack-compilers:
 
@@ -281,7 +282,7 @@ your ``PATH``.
 ``spack compilers``
 ^^^^^^^^^^^^^^^^^^^
 
-You can see which compilers spack has found by running ``spack
+You can see which compilers are available to Spack by running ``spack
 compilers`` or ``spack compiler list``:
 
 .. code-block:: console
@@ -320,9 +321,10 @@ An alias for ``spack compiler find``.
 ``spack compiler find``
 ^^^^^^^^^^^^^^^^^^^^^^^
 
-If you do not see a compiler in this list, but you want to use it with
-Spack, you can simply run ``spack compiler find`` with the path to
-where the compiler is installed.  For example:
+Lists the compilers currently available to Spack. If you do not see
+a compiler in this list, but you want to use it with Spack, you can
+simply run ``spack compiler find`` with the path to where the
+compiler is installed.  For example:
 
 .. code-block:: console