docs: add --depth=2 to reduce download size (spack#46605)

* docs: add --depth=2 to reduce download size

* Add note to tell users about --depth=2 and manyFiles

* Fix inline code in info block

README.md

@@ -46,13 +46,18 @@ See the
 [Feature Overview](https://spack.readthedocs.io/en/latest/features.html)
 for examples and highlights.
 
-To install spack and your first package, make sure you have Python.
+To install spack and your first package, make sure you have Python & Git.
 Then:
 
-    $ git clone -c feature.manyFiles=true https://github.com/spack/spack.git
+    $ git clone -c feature.manyFiles=true --depth=2 https://github.com/spack/spack.git
     $ cd spack/bin
     $ ./spack install zlib
 
+> [!TIP]
+> `-c feature.manyFiles=true` improves git's performance on repositories with 1,000+ files.
+>
+> `--depth=2` prunes the git history to reduce the size of the Spack installation.
+
 Documentation
 ----------------
 

lib/spack/docs/getting_started.rst

@@ -61,10 +61,15 @@ Getting Spack is easy.  You can clone it from the `github repository
 
 .. code-block:: console
 
-   $ git clone -c feature.manyFiles=true https://github.com/spack/spack.git
+   $ git clone -c feature.manyFiles=true --depth=2 https://github.com/spack/spack.git
 
 This will create a directory called ``spack``.
 
+.. note::
+   ``-c feature.manyFiles=true`` improves git's performance on repositories with 1,000+ files.
+
+   ``--depth=2`` prunes the git history to reduce the size of the Spack installation.
+
 .. _shell-support:
 
 ^^^^^^^^^^^^^
@@ -1576,4 +1581,3 @@ The intent is to provide a Windows installer that will automatically set up
 Python, Git, and Spack, instead of requiring the user to do so manually.
 Instructions for creating the installer are at
 https://github.com/spack/spack/blob/develop/lib/spack/spack/cmd/installer/README.md
-

lib/spack/docs/index.rst

@@ -39,10 +39,15 @@ package:
 
 .. code-block:: console
 
-   $ git clone -c feature.manyFiles=true https://github.com/spack/spack.git
+   $ git clone -c feature.manyFiles=true --depth=2 https://github.com/spack/spack.git
    $ cd spack/bin
    $ ./spack install libelf
 
+.. note::
+   ``-c feature.manyFiles=true`` improves git's performance on repositories with 1,000+ files.
+
+   ``--depth=2`` prunes the git history to reduce the size of the Spack installation.
+
 If you're new to spack and want to start using it, see :doc:`getting_started`,
 or refer to the full manual below.