add charliecloud 0.16 (#16810)

* add charliecloud/0.16

* tidy comments

var/spack/repos/builtin/packages/charliecloud/package.py

@@ -9,12 +9,13 @@
 class Charliecloud(AutotoolsPackage):
     """Lightweight user-defined software stacks for HPC."""
 
-    maintainers = ['j-ogas']
+    maintainers = ['j-ogas', 'reidpr']
     homepage = "https://hpc.github.io/charliecloud"
     url      = "https://github.com/hpc/charliecloud/releases/download/v0.14/charliecloud-0.14.tar.gz"
     git      = "https://github.com/hpc/charliecloud.git"
 
     version('master', branch='master')
+    version('0.16',   sha256='6cdc21d414b6173090ac0a4c2c62a2a038c81659a75ae8f837b332bb7e6e9090')
     version('0.15',   sha256='2163420d43c934151c4f44a188313bdb7f79e576d5a86ba64b9ea45f784b9921')
     version('0.14',   sha256='4ae23c2d6442949e16902f9d5604dbd1d6059aeb5dd461b11fc5c74d49dcb194')
     version('0.13',   sha256='5740bff6e410ca99484c1bdf3dbe834c0f753c846d55c19d6162967a3e2718e0')
@@ -24,25 +25,26 @@ class Charliecloud(AutotoolsPackage):
     depends_on('automake', type='build')
     depends_on('libtool',  type='build')
 
-    # Use skopeo and umoci for older ch-grow version dependencies
+    # Use skopeo and umoci for older ch-grow version dependencies.
     depends_on('skopeo',         type='run', when='@0.10:0.13')
     depends_on('umoci',          type='run', when='@0.10:0.13')
     depends_on('python+libxml2', type='run', when='@0.10:0.13')
 
-    # Charliecloud@0.14 and up use python for building
+    # Use python for ch-grow 0.14 and above version dependencies.
     depends_on('python@3.5:',    type='run', when='@0.14:')
     depends_on('py-lark-parser', type='run', when='@0.14:')
     depends_on('py-requests',    type='run', when='@0.14:')
 
-    # man pages and html docs variant
+    # Man pages and html docs variant.
     variant('docs', default=False, description='Build man pages and html docs')
     depends_on('rsync',               type='build', when='+docs')
     depends_on('py-sphinx',           type='build', when='+docs')
     depends_on('py-sphinx-rtd-theme', type='build', when='+docs')
 
+    # See https://github.com/spack/spack/pull/16049.
     conflicts('platform=darwin', msg='This package does not build on macOS')
 
-    # bash automated testing harness (bats)
+    # Bash automated testing harness (bats).
     depends_on('bats@0.4.0', type='test')
     depends_on('python@3.5:', type='test')