docs: git version section title + highlight issues (#42398)

* basic_usage: section title for git versions

* improve highlighting by using a comment instead of invalid syntax

lib/spack/docs/basic_usage.rst

@@ -1130,6 +1130,10 @@ A version specifier can also be a list of ranges and specific versions,
 separated by commas.  For example, ``@1.0:1.5,=1.7.1`` matches any version
 in the range ``1.0:1.5`` and the specific version ``1.7.1``.
 
+^^^^^^^^^^^^
+Git versions
+^^^^^^^^^^^^
+
 For packages with a ``git`` attribute, ``git`` references
 may be specified instead of a numerical version i.e. branches, tags
 and commits. Spack will stage and build based off the ``git``

lib/spack/docs/environments.rst

@@ -472,11 +472,11 @@ a ``packages.yaml`` file) could contain:
 .. code-block:: yaml
 
    spack:
-     ...
+     # ...
      packages:
        all:
          compiler: [intel]
-     ...
+     # ...
 
 This configuration sets the default compiler for all packages to
 ``intel``.
@@ -822,7 +822,7 @@ directories.
 .. code-block:: yaml
 
    spack:
-     ...
+     # ...
      view:
        mpis:
          root: /path/to/view
@@ -866,7 +866,7 @@ automatically named ``default``, so that
 .. code-block:: yaml
 
    spack:
-     ...
+     # ...
      view: True
 
 is equivalent to
@@ -874,7 +874,7 @@ is equivalent to
 .. code-block:: yaml
 
    spack:
-     ...
+     # ...
      view:
        default:
          root: .spack-env/view
@@ -884,7 +884,7 @@ and
 .. code-block:: yaml
 
    spack:
-     ...
+     # ...
      view: /path/to/view
 
 is equivalent to
@@ -892,7 +892,7 @@ is equivalent to
 .. code-block:: yaml
 
    spack:
-     ...
+     # ...
      view:
        default:
          root: /path/to/view

lib/spack/docs/getting_started.rst

@@ -623,7 +623,7 @@ Fortran.
 
       compilers:
       - compiler:
-        ...
+        # ...
         paths:
           cc: /usr/bin/clang
           cxx: /usr/bin/clang++

lib/spack/docs/module_file_support.rst

@@ -198,7 +198,7 @@ set by changing the ``roots`` key of the configuration.
      my_custom_lmod_modules:
        roots:
          lmod: /path/to/install/custom/lmod/modules
-         ...
+         # ...
 
 This configuration will create two module sets. The default module set
 will install its ``tcl`` modules to ``/path/to/install/tcl/modules``

lib/spack/docs/pipelines.rst

@@ -810,7 +810,7 @@ generated by ``spack ci generate``.  You also want your generated rebuild jobs
 .. code-block:: yaml
 
    spack:
-     ...
+     # ...
      ci:
        pipeline-gen:
        - build-job: