Add note to docs for selecting branch when cloning (JCSDA#1341)

doc/source/NewSiteConfigs.rst

@@ -211,11 +211,11 @@ Creating a new environment
 
 Remember to activate the ``lua`` module environment and have MacTeX in your search path, if applicable. It is also recommended to increase the stacksize limit to 65Kb using ``ulimit -S -s unlimited``.
 
-1. You will need to clone spack-stack and its dependencies and activate the spack-stack tool. It is also a good idea to save the directory in your environment for later use.
+1. You will need to clone spack-stack (selecting your desired spack-stack branch) and its dependencies and activate the spack-stack tool. It is also a good idea to save the directory in your environment for later use.
 
 .. code-block:: console
 
-   git clone --recurse-submodules https://github.com/jcsda/spack-stack.git
+   git clone [-b develop OR release/branch-name] --recurse-submodules https://github.com/jcsda/spack-stack.git
    cd spack-stack
 
    # Sources Spack from submodule and sets ${SPACK_STACK_DIR}
@@ -500,11 +500,11 @@ Creating a new environment
 
 It is recommended to increase the stacksize limit by using ``ulimit -S -s unlimited``, and to test if the module environment functions correctly (``module available``).
 
-1. You will need to clone spack-stack and its dependencies and activate the spack-stack tool. It is also a good idea to save the directory in your environment for later use.
+1. You will need to clone spack-stack (selecting your desired spack-stack branch) and its dependencies and activate the spack-stack tool. It is also a good idea to save the directory in your environment for later use.
 
 .. code-block:: console
 
-   git clone --recurse-submodules https://github.com/jcsda/spack-stack.git
+   git clone [-b develop OR release/branch-name] --recurse-submodules https://github.com/jcsda/spack-stack.git
    cd spack-stack
 
    # Sources Spack from submodule and sets ${SPACK_STACK_DIR}
@@ -675,11 +675,11 @@ With all of that in mind, the following instructions were used on an Amazon Web
    module use /opt/nvidia/hpc_sdk/modulefiles
    module load nvhpc-openmpi3/24.3
 
-4. Clone spack-stack and its dependencies and activate the spack-stack tool.
+4. Clone spack-stack (selecting your desired spack-stack branch) and its dependencies and activate the spack-stack tool.
 
 .. code-block:: console
 
-   git clone --recurse-submodules https://github.com/jcsda/spack-stack.git
+   git clone [-b develop OR release/branch-name] --recurse-submodules https://github.com/jcsda/spack-stack.git
    cd spack-stack
 
    # Sources Spack from submodule and sets ${SPACK_STACK_DIR}