commands: add spack resource command to inspect downloadable files

- currently just looks at patches
  - allows you to find out which package applied a patch to a spec

- intended to work with tarballs and resources in the future.

- add tab completion for `spack resource` and subcommands

lib/spack/docs/packaging_guide.rst

@@ -1422,6 +1422,73 @@ with all packages in Spack, a patched dependency library can coexist with
 other versions of that library.  See the `section on depends_on
 <dependency_dependency_patching_>`_ for more details.
 
+.. _patch_inspecting_patches:
+
+^^^^^^^^^^^^^^^^^^^
+Inspecting patches
+^^^^^^^^^^^^^^^^^^^
+
+If you want to better understand the patches that Spack applies to your
+packages, you can do that using ``spack spec``, ``spack find``, and other
+query commands.  Let's look at ``m4``.  If you run ``spack spec m4``, you
+can see the patches that would be applied to ``m4``::
+
+  $ spack spec m4
+  Input spec
+  --------------------------------
+  m4
+
+  Concretized
+  --------------------------------
+  m4@1.4.18%clang@9.0.0-apple patches=3877ab548f88597ab2327a2230ee048d2d07ace1062efe81fc92e91b7f39cd00,c0a408fbffb7255fcc75e26bd8edab116fc81d216bfd18b473668b7739a4158e,fc9b61654a3ba1a8d6cd78ce087e7c96366c290bc8d2c299f09828d793b853c8 +sigsegv arch=darwin-highsierra-x86_64
+      ^libsigsegv@2.11%clang@9.0.0-apple arch=darwin-highsierra-x86_64
+
+You can also see patches that have been applied to installed packages
+with ``spack find -v``::
+
+  $ spack find -v m4
+  ==> 1 installed package
+  -- darwin-highsierra-x86_64 / clang@9.0.0-apple -----------------
+  m4@1.4.18 patches=3877ab548f88597ab2327a2230ee048d2d07ace1062efe81fc92e91b7f39cd00,c0a408fbffb7255fcc75e26bd8edab116fc81d216bfd18b473668b7739a4158e,fc9b61654a3ba1a8d6cd78ce087e7c96366c290bc8d2c299f09828d793b853c8 +sigsegv
+
+.. _cmd-spack-resource:
+
+In both cases above, you can see that the patches' sha256 hashes are
+stored on the spec as a variant.  As mentioned above, this means that you
+can have multiple, differently-patched versions of a package installed at
+once.
+
+You can look up a patch by its sha256 hash (or a short version of it)
+using the ``spack resource show`` command::
+
+  $ spack resource show 3877ab54
+  3877ab548f88597ab2327a2230ee048d2d07ace1062efe81fc92e91b7f39cd00
+      path:       /home/spackuser/src/spack/var/spack/repos/builtin/packages/m4/gnulib-pgi.patch
+      applies to: builtin.m4
+
+``spack resource show`` looks up downloadable resources from package
+files by hash and prints out information about them.  Above, we see that
+the ``3877ab54`` patch applies to the ``m4`` package.  The output also
+tells us where to find the patch.
+
+Things get more interesting if you want to know about dependency
+patches. For example, when ``dealii`` is built with ``boost@1.68.0``, it
+has to patch boost to work correctly.  If you didn't know this, you might
+wonder where the extra boost patches are coming from::
+
+  $ spack spec dealii ^boost@1.68.0 ^hdf5+fortran | grep '\^boost'
+      ^boost@1.68.0
+          ^boost@1.68.0%clang@9.0.0-apple+atomic+chrono~clanglibcpp cxxstd=default +date_time~debug+exception+filesystem+graph~icu+iostreams+locale+log+math~mpi+multithreaded~numpy patches=2ab6c72d03dec6a4ae20220a9dfd5c8c572c5294252155b85c6874d97c323199,b37164268f34f7133cbc9a4066ae98fda08adf51e1172223f6a969909216870f ~pic+program_options~python+random+regex+serialization+shared+signals~singlethreaded+system~taggedlayout+test+thread+timer~versionedlayout+wave arch=darwin-highsierra-x86_64
+  $ spack resource show b37164268
+  b37164268f34f7133cbc9a4066ae98fda08adf51e1172223f6a969909216870f
+      path:       /home/spackuser/src/spack/var/spack/repos/builtin/packages/dealii/boost_1.68.0.patch
+      applies to: builtin.boost
+      patched by: builtin.dealii
+
+Here you can see that the patch is applied to ``boost`` by ``dealii``,
+and that it lives in ``dealii``'s directory in Spack's ``builtin``
+package repository.
+
 .. _handling_rpaths:
 
 ---------------

lib/spack/spack/cmd/resource.py

@@ -0,0 +1,84 @@
+# Copyright 2013-2018 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from __future__ import print_function
+import os
+
+import llnl.util.tty as tty
+import llnl.util.tty.color as color
+
+import spack.repo
+
+
+description = "list downloadable resources (tarballs, repos, patches, etc.)"
+section = "basic"
+level = "long"
+
+
+def setup_parser(subparser):
+    sp = subparser.add_subparsers(
+        metavar='SUBCOMMAND', dest='resource_command')
+
+    list_parser = sp.add_parser('list', help=resource_list.__doc__)
+    list_parser.add_argument('--only-hashes', action='store_true',
+                             help='only print sha256 hashes of resources')
+
+    show_parser = sp.add_parser('show', help=resource_show.__doc__)
+    show_parser.add_argument('hash', action='store')
+
+
+def _show_patch(sha256):
+    """Show a record from the patch index."""
+    patches = spack.repo.path.patch_index.index
+    data = patches.get(sha256)
+
+    if not data:
+        candidates = [k for k in patches if k.startswith(sha256)]
+        if not candidates:
+            tty.die('no such resource: %s' % sha256)
+        elif len(candidates) > 1:
+            tty.die('%s: ambiguous hash prefix. Options are:',
+                    *candidates)
+
+        sha256 = candidates[0]
+        data = patches.get(sha256)
+
+    color.cprint('@c{%s}' % sha256)
+    for package, rec in data.items():
+        owner = rec['owner']
+
+        if 'relative_path' in rec:
+            pkg_dir = spack.repo.get(owner).package_dir
+            path = os.path.join(pkg_dir, rec['relative_path'])
+            print("    path:       %s" % path)
+        else:
+            print("    url:        %s" % rec['url'])
+
+        print("    applies to: %s" % package)
+        if owner != package:
+            print("    patched by: %s" % owner)
+
+
+def resource_list(args):
+    """list all resources known to spack (currently just patches)"""
+    patches = spack.repo.path.patch_index.index
+    for sha256 in patches:
+        if args.only_hashes:
+            print(sha256)
+        else:
+            _show_patch(sha256)
+
+
+def resource_show(args):
+    """show a resource, identified by its checksum"""
+    _show_patch(args.hash)
+
+
+def resource(parser, args):
+    action = {
+        'list': resource_list,
+        'show': resource_show
+    }
+    action[args.resource_command](args)

lib/spack/spack/test/cmd/resource.py

@@ -0,0 +1,60 @@
+# Copyright 2013-2018 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+from spack.main import SpackCommand
+
+
+resource = SpackCommand('resource')
+
+#: these are hashes used in mock packages
+mock_hashes = [
+    'abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234',
+    '1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd1234abcd',
+    'b5bb9d8014a0f9b1d61e21e796d78dccdf1352f23cd32812f4850b878ae4944c',
+    'c45c1564f70def3fc1a6e22139f62cb21cd190cc3a7dbe6f4120fa59ce33dcb8',
+    '24eceabef5fe8f575ff4b438313dc3e7b30f6a2d1c78841fbbe3b9293a589277',
+    '689b8f9b32cb1d2f9271d29ea3fca2e1de5df665e121fca14e1364b711450deb',
+    'ebe27f9930b99ebd8761ed2db3ea365142d0bafd78317efb4baadf62c7bf94d0',
+    '208fcfb50e5a965d5757d151b675ca4af4ce2dfd56401721b6168fae60ab798f',
+    'bf07a7fbb825fc0aae7bf4a1177b2b31fcf8a3feeaf7092761e18c859ee52a9c',
+    '7d865e959b2466918c9863afca942d0fb89d7c9ac0c99bafc3749504ded97730',
+]
+
+
+def test_resource_list(mock_packages, capfd):
+    with capfd.disabled():
+        out = resource('list')
+
+    for h in mock_hashes:
+        assert h in out
+
+    assert 'url:' in out
+    assert 'applies to:' in out
+    assert 'patched by:' in out
+    assert 'path:' in out
+
+    assert 'repos/builtin.mock/packages/patch-a-dependency/libelf.patch' in out
+    assert 'applies to: builtin.mock.libelf' in out
+    assert 'patched by: builtin.mock.patch-a-dependency' in out
+
+
+def test_resource_list_only_hashes(mock_packages, capfd):
+    with capfd.disabled():
+        out = resource('list', '--only-hashes')
+
+    for h in mock_hashes:
+        assert h in out
+
+
+def test_resource_show(mock_packages, capfd):
+    with capfd.disabled():
+        out = resource('show', 'c45c1564f70def3fc1a6e22139f62cb21cd190cc3a7dbe6f4120fa59ce33dcb8')
+
+    assert out.startswith('c45c1564f70def3fc1a6e22139f62cb21cd190cc3a7dbe6f4120fa59ce33dcb8')
+    assert 'repos/builtin.mock/packages/patch-a-dependency/libelf.patch' in out
+    assert 'applies to: builtin.mock.libelf' in out
+    assert 'patched by: builtin.mock.patch-a-dependency' in out
+
+    assert len(out.strip().split('\n')) == 4

share/spack/spack-completion.bash

@@ -1041,6 +1041,28 @@ function _spack_repo_rm {
     _spack_repo_remove
 }
 
+function _spack_resource {
+    if $list_options
+    then
+        compgen -W "-h --help" -- "$cur"
+    else
+        compgen -W "list show" -- "$cur"
+    fi
+}
+
+function _spack_resource_list {
+    compgen -W "-h --help --only-hashes" -- "$cur"
+}
+
+function _spack_resource_show {
+    if $list_options
+    then
+        compgen -W "-h --help" -- "$cur"
+    else
+        compgen -W "$(_all_resource_hashes)" -- "$cur"
+    fi
+}
+
 function _spack_restage {
     if $list_options
     then
@@ -1244,6 +1266,10 @@ function _all_packages {
     spack list
 }
 
+function _all_resource_hashes {
+    spack resource list --only-hashes
+}
+
 function _installed_packages {
     spack --color=never find | grep -v "^--"
 }