Fix replace os vars functionality

The first run would correctly replace the environment
variables, however it would also overwrite the original
vm.args and sys.config thus preventing any further
substitution in subsequent runs.
Dev mode runs were also broken, all runs after the
first were required to also define the
RELX_REPLACE_OS_VARS variable in order not to
overwrite the current vm.args with the original one,
this prevented simply attaching to an already running
node that was started this way.

Add tests to exercise this functionality.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/rlx_prv_overlay.erl b/src/rlx_prv_overlay.erl
index 71aca97..a4c0fa4 100644
--- a/src/rlx_prv_overlay.erl
+++ b/src/rlx_prv_overlay.erl
@@ -461,6 +461,14 @@ write_template(OverlayVars, FromFile, ToFile) ->
                 {ok, IoData} ->
                     case filelib:ensure_dir(ToFile) of
                         ok ->
+                            %% we were asked to render a template
+                            %% onto a symlink, this would cause an overwrite
+                            %% of the original file, so we delete the symlink
+                            %% and go ahead with the template render
+                            case ec_file:is_symlink(ToFile) of
+                                true -> ec_file:remove(ToFile);
+                                false -> ok
+                            end,
                             case file:write_file(ToFile, IoData) of
                                 ok ->
                                     {ok, FileInfo} = file:read_file_info(FromFile),