Move remaining core tasks to core_tasks.

Still not moved: GroupTask, which we're killing, and
targets_help+builddictionary, which I want to rewrite, because
they currently use old, clunky code with waaay too many deps.

Testing Done:
CI passes: https://travis-ci.org/pantsbuild/pants/builds/94525012

Reviewed at https://rbcommons.com/s/twitter/r/3204/

src/python/pants/backend/core/register.py

@@ -12,16 +12,12 @@
 from pants.backend.core.targets.doc import Page, Wiki, WikiArtifact
 from pants.backend.core.targets.prep_command import PrepCommand
 from pants.backend.core.targets.resources import Resources
-from pants.backend.core.tasks.bash_completion import BashCompletionTask
 from pants.backend.core.tasks.builddictionary import BuildBuildDictionary
 from pants.backend.core.tasks.cloc import CountLinesOfCode
 from pants.backend.core.tasks.confluence_publish import ConfluencePublish
-from pants.backend.core.tasks.deferred_sources_mapper import DeferredSourcesMapper
 from pants.backend.core.tasks.dependees import ReverseDepmap
-from pants.backend.core.tasks.explain_options_task import ExplainOptionsTask
 from pants.backend.core.tasks.filemap import Filemap
 from pants.backend.core.tasks.filter import Filter
-from pants.backend.core.tasks.list_goals import ListGoals
 from pants.backend.core.tasks.list_owners import ListOwners
 from pants.backend.core.tasks.listtargets import ListTargets
 from pants.backend.core.tasks.markdown_to_html import MarkdownToHtml
@@ -80,7 +76,6 @@ def register_goals():
   # with_description() removed, as their docstring will be used instead.
 
   # Getting help.
-  task(name='goals', action=ListGoals).install().with_description('List all documented goals.')
 
   task(name='targets', action=TargetsHelp).install().with_description(
       'List target types and BUILD file symbols (python_tests, jar, etc).')
@@ -123,12 +118,3 @@ def register_goals():
 
   task(name='list-owners', action=ListOwners).install().with_description(
       'Print targets that own the specified source')
-
-  task(name='deferred-sources', action=DeferredSourcesMapper).install().with_description(
-    'Map unpacked sources from archives.')
-
-  task(name='bash-completion', action=BashCompletionTask).install().with_description(
-    'Dump bash shell script for autocompletion of pants command lines.')
-
-  task(name='options', action=ExplainOptionsTask).install().with_description(
-    'List what options pants has set.')

src/python/pants/backend/core/tasks/BUILD

@@ -42,18 +42,14 @@ python_library(
 target(
   name = 'all',
   dependencies = [
-    ':bash_completion',
     ':builddictionary',
     ':cloc',
     ':confluence_publish',
     ':console_task',
-    ':deferred_sources_mapper',
     ':dependees',
-    ':explain_options',
     ':filemap',
     ':filter',
     ':group_task',
-    ':list_goals',
     ':list_owners',
     ':listtargets',
     ':markdown_to_html',
@@ -68,27 +64,6 @@ target(
   ]
 )
 
-python_library(
-  name = 'bash_completion',
-  sources = ['bash_completion.py'],
-  resource_targets = [
-    ':bash_completion_resources',
-  ],
-  dependencies = [
-    'src/python/pants/base:exceptions',
-    'src/python/pants/base:generator',
-    'src/python/pants/goal',
-    'src/python/pants/help',
-    'src/python/pants/option',
-    'src/python/pants/task',
-  ],
-)
-
-resources(
-  name = 'bash_completion_resources',
-  sources = globs('templates/bash_completion/*.mustache'),
-)
-
 python_library(
   name = 'builddictionary',
   sources = ['builddictionary.py'],
@@ -143,16 +118,6 @@ python_library(
   ],
 )
 
-python_library(
-  name = 'deferred_sources_mapper',
-  sources= ['deferred_sources_mapper.py'],
-  dependencies = [
-    'src/python/pants/base:payload_field',
-    'src/python/pants/build_graph',
-    'src/python/pants/task',
-  ],
-)
-
 python_library(
   name = 'dependees',
   sources = ['dependees.py'],
@@ -163,16 +128,6 @@ python_library(
   ],
 )
 
-python_library(
-  name = 'explain_options',
-  sources = ['explain_options_task.py'],
-  dependencies = [
-    '3rdparty/python:ansicolors',
-    'src/python/pants/option',
-    'src/python/pants/task',
-  ],
-)
-
 python_library(
   name = 'filemap',
   sources = ['filemap.py'],
@@ -208,15 +163,6 @@ python_library(
   ],
 )
 
-python_library(
-  name = 'list_goals',
-  sources = ['list_goals.py'],
-  dependencies = [
-    'src/python/pants/goal',
-    'src/python/pants/task',
-  ],
-)
-
 python_library(
   name = 'listtargets',
   sources = ['listtargets.py'],
@@ -301,9 +247,8 @@ python_library(
   name = 'scm_publish',
   sources = ['scm_publish.py'],
   dependencies = [
-    'src/python/pants/base:exceptions',
-    'src/python/pants/option',
-    'src/python/pants/scm',
+    'src/python/pants/base:deprecated',
+    'src/python/pants/task',
   ],
 )