Plugin templates enabled

This lets a plugin define templates to be loaded:

    $ rebar3 new
    ...
    proper (plugin): A basic PropEr suite for an OTP application
    ...
    $ rebar3 new help proper
    proper:
            plugin template (...)
            Description: A basic PropEr suite for an OTP application
            Variables:
                    name="suite" (...)
                    ...
    → rebar3 new proper fakesuite
    ===> Writing test/prop_fakesuite.erl

In this case, proper is a fake template file I've put by hand in
_build/default/plugins/rebar3_proper/priv/<somename>/, meaning it will
only work as far as it's called from the project's root.

The priority order of plugins is now .config > plugin > built-in, such
that someone could ensure plugins do not crush their own private
templates, but also that custom or plugin templates do overtake built-in
ones. It used to be Built-in > .config only.

Templates are searched for recursively in the priv/ directory of
plugins.

2 files changed, 28 insertions, 0 deletions

diff --git a/test/rebar_new_SUITE_data/plugin_tpl/src/plugin_tpl.app.src b/test/rebar_new_SUITE_data/plugin_tpl/src/plugin_tpl.app.src
new file mode 100644
index 0000000..8f18874
--- /dev/null
+++ b/test/rebar_new_SUITE_data/plugin_tpl/src/plugin_tpl.app.src
@@ -0,0 +1,15 @@
+{application, 'plugin_tpl',
+ [{description, "An OTP library"},
+  {vsn, "0.1.0"},
+  {registered, []},
+  {applications,
+   [kernel,
+    stdlib
+   ]},
+  {env,[]},
+  {modules, []},
+
+  {contributors, []},
+  {licenses, []},
+  {links, []}
+ ]}.
diff --git a/test/rebar_new_SUITE_data/plugin_tpl/src/plugin_tpl.erl b/test/rebar_new_SUITE_data/plugin_tpl/src/plugin_tpl.erl
new file mode 100644
index 0000000..406bd97
--- /dev/null
+++ b/test/rebar_new_SUITE_data/plugin_tpl/src/plugin_tpl.erl
@@ -0,0 +1,13 @@
+-module('plugin_tpl').
+
+%% API exports
+-export([]).
+
+%%====================================================================
+%% API functions
+%%====================================================================
+
+
+%%====================================================================
+%% Internal functions
+%%====================================================================