Migrate to an umbrella structure

This is a prerequisite for vendoring and demands that we move all source
files around, and update the helper scripts (like bootstrap) to work
with it.

This should have no consequence on rebar3 users aside from needing to
fetch a git_subdir if they need the content for it.

.gitignore

@@ -24,4 +24,4 @@ ebin
 env
 
 # hex_core artifact
-src/vendored/r3_safe_erl_term.erl
+apps/rebar/src/vendored/r3_safe_erl_term.erl

apps/rebar/rebar.config

@@ -0,0 +1,90 @@
+%% -*- mode: erlang;erlang-indent-level: 4;indent-tabs-mode: nil -*-
+%% ex: ts=4 sw=4 ft=erlang et
+
+{deps, [{erlware_commons,  "1.5.0"},
+        {ssl_verify_fun,   "1.1.6"},
+        {certifi,          "2.9.0"},
+        {providers,        "1.9.0"},
+        {getopt,           "1.0.1"},
+        {bbmustache,       "1.12.2"},
+        {relx,             "4.7.0"},
+        {cf,               "0.3.1"},
+        {cth_readable,     "1.5.1"},
+        {eunit_formatters, "0.5.0"}]}.
+
+{post_hooks, [{"(linux|darwin|solaris|freebsd|netbsd|openbsd)",
+               escriptize,
+               "cp \"$REBAR_BUILD_DIR/bin/rebar3\" ./rebar3"},
+              {"win32",
+               escriptize,
+               "robocopy \"%REBAR_BUILD_DIR%/bin/\" ./ rebar3* "
+               "/njs /njh /nfl /ndl & exit /b 0"} % silence things
+             ]}.
+
+{escript_name, rebar3}.
+{escript_wrappers_windows, ["cmd", "powershell"]}.
+{escript_comment, "%%Rebar3 3.19.0\n"}.
+{escript_emu_args, "%%! +sbtu +A1\n"}.
+%% escript_incl_priv is for internal rebar-private use only.
+%% Do not use outside rebar. Config interface is not stable.
+{escript_incl_priv, [{relx, "templates/*"},
+                     {rebar, "templates/*"}]}.
+
+{overrides, [{add, relx, [{erl_opts, [{d, 'RLX_LOG', rebar_log}]}]}]}.
+
+{erl_opts, [warnings_as_errors,
+            {platform_define, "^(2[1-9])|(20\\\\.3)", filelib_find_source},
+            {platform_define, "^(1|(20))", no_customize_hostname_check},
+            {platform_define, "^(20)", fun_stacktrace}
+           ]}.
+
+{edoc_opts, [preprocess]}.
+
+%% Use OTP 23+ when dialyzing rebar3
+{dialyzer, [
+    {warnings, [unknown]},
+    {plt_extra_apps, [parsetools, public_key]}
+]}.
+
+%% Keep only the logs of the last 5 runs
+{ct_opts, [{keep_logs, 5}]}.
+
+%% Profiles
+{profiles, [{test, [
+                   {deps, [{meck, "0.8.13"}]},
+                   {erl_opts, [debug_info, nowarn_export_all]}
+                   ]
+            },
+
+            {dialyzer, [
+                {erl_opts, [debug_info, nowarn_export_all]}
+            ]},
+
+            {bootstrap, []},
+
+            {prod, [
+                {erl_opts, [no_debug_info]},
+                {overrides, [
+                    {override, erlware_commons, [
+                        {erl_opts, [{platform_define, "^[0-9]+", namespaced_types},
+                                    {platform_define, "^R1[4|5]", deprecated_crypto},
+                                    {platform_define, "^((1[8|9])|2)", rand_module},
+                                    {platform_define, "^2", unicode_str},
+                                    {platform_define, "^(R|1|20)", fun_stacktrace},
+                                    no_debug_info,
+                                    warnings_as_errors]},
+                        {deps, []}, {plugins, []}]},
+                    {add, ssl_verify_hostname, [{erl_opts, [no_debug_info]}]},
+                    {add, certifi, [{erl_opts, [no_debug_info]}]},
+                    {add, cf, [{erl_opts, [no_debug_info]}]},
+                    {add, cth_readable, [{erl_opts, [no_debug_info]}]},
+                    {add, eunit_formatters, [{erl_opts, [no_debug_info]}]},
+                    {override, bbmustache, [
+                        {erl_opts, [no_debug_info, {platform_define, "^[0-9]+", namespaced_types}]},
+                        {deps, []}, {plugins, []}]},
+                    {add, getopt, [{erl_opts, [no_debug_info]}]},
+                    {add, providers, [{erl_opts, [no_debug_info]}]},
+                    {add, relx, [{erl_opts, [no_debug_info]}]}]}
+            ]}
+           ]}.
+