Resync helpers from trunk

Makefile

@@ -1,8 +1,8 @@
 #!/usr/bin/make
 
 lint:
-	flake8 --exclude hooks/charmhelpers hooks
-	charm proof
+	@flake8 --exclude hooks/charmhelpers hooks
+	@charm proof
 
 sync:
-	charm-helper-sync -c charm-helpers-sync.yaml
+	@charm-helper-sync -c charm-helpers-sync.yaml

charm-helpers-sync.yaml

@@ -1,4 +1,4 @@
-branch: lp:~james-page/charm-helpers/configure_source_redux
+branch: lp:charm-helpers
 destination: hooks/charmhelpers
 include:
     - core

hooks/charmhelpers/core/hookenv.py

@@ -333,3 +333,6 @@ class Hooks(object):
                 self.register(decorated.__name__, decorated)
             return decorated
         return wrapper
+
+def charm_dir():
+    return os.environ.get('CHARM_DIR')

hooks/charmhelpers/fetch/__init__.py

@@ -1,11 +1,21 @@
+import importlib
 from yaml import safe_load
-from charmhelpers.core.hookenv import config
 from charmhelpers.core.host import (
-    apt_install, apt_update, filter_installed_packages
+    apt_install,
+    apt_update,
+    filter_installed_packages
+)
+from urlparse import (
+    urlparse,
+    urlunparse,
 )
 import subprocess
+from charmhelpers.core.hookenv import (
+    config,
+    log,
+)
 
-CLOUD_ARCHIVE = """ # Ubuntu Cloud Archive
+CLOUD_ARCHIVE = """# Ubuntu Cloud Archive
 deb http://ubuntu-cloud.archive.canonical.com/ubuntu {} main
 """
 
@@ -56,3 +66,79 @@ def configure_sources(update=False,
             add_source(sources[src_num], keys[src_num])
     if update:
         apt_update(fatal=True)
+
+# The order of this list is very important. Handlers should be listed in from
+# least- to most-specific URL matching.
+FETCH_HANDLERS = (
+    'charmhelpers.fetch.archiveurl.ArchiveUrlFetchHandler',
+)
+
+
+class UnhandledSource(Exception):
+    pass
+
+
+def install_remote(source):
+    """
+    Install a file tree from a remote source
+
+    The specified source should be a url of the form:
+        scheme://[host]/path[#[option=value][&...]]
+
+    Schemes supported are based on this modules submodules
+    Options supported are submodule-specific"""
+    # We ONLY check for True here because can_handle may return a string
+    # explaining why it can't handle a given source.
+    handlers = [h for h in plugins() if h.can_handle(source) is True]
+    for handler in handlers:
+        try:
+            installed_to = handler.install(source)
+        except UnhandledSource:
+            pass
+    if not installed_to:
+        raise UnhandledSource("No handler found for source {}".format(source))
+    return installed_to
+
+
+def install_from_config(config_var_name):
+    charm_config = config()
+    source = charm_config[config_var_name]
+    return install_remote(source)
+
+
+class BaseFetchHandler(object):
+    """Base class for FetchHandler implementations in fetch plugins"""
+    def can_handle(self, source):
+        """Returns True if the source can be handled. Otherwise returns
+        a string explaining why it cannot"""
+        return "Wrong source type"
+
+    def install(self, source):
+        """Try to download and unpack the source. Return the path to the
+        unpacked files or raise UnhandledSource."""
+        raise UnhandledSource("Wrong source type {}".format(source))
+
+    def parse_url(self, url):
+        return urlparse(url)
+
+    def base_url(self, url):
+        """Return url without querystring or fragment"""
+        parts = list(self.parse_url(url))
+        parts[4:] = ['' for i in parts[4:]]
+        return urlunparse(parts)
+
+
+def plugins(fetch_handlers=None):
+    if not fetch_handlers:
+        fetch_handlers = FETCH_HANDLERS
+    plugin_list = []
+    for handler_name in fetch_handlers:
+        package, classname = handler_name.rsplit('.', 1)
+        try:
+            handler_class = getattr(importlib.import_module(package), classname)
+            plugin_list.append(handler_class())
+        except (ImportError, AttributeError):
+            # Skip missing plugins so that they can be ommitted from
+            # installation if desired
+            log("FetchHandler {} not found, skipping plugin".format(handler_name))
+    return plugin_list