fix(ci): Populate elixir vsn from env at build time (#7773)

Dependabot's workflow is set up in such a way it seems that it can't
find our `sha.exs` file.

This is a cleaner approach that doesn't rely on using external files for
the application version.

Interesting note: `mix compile` will happily use the cached `version`
even though it's computed from an env var, because `mix compile` uses
file hash and mtime to know when to recompile.

See https://github.com/firezone/firezone/network/updates/942719116

elixir/Dockerfile

@@ -226,10 +226,10 @@ COPY apps/domain/mix.exs ./apps/domain/mix.exs
 COPY apps/web/mix.exs ./apps/web/mix.exs
 COPY apps/api/mix.exs ./apps/api/mix.exs
 COPY config config
-COPY sha.exs .
 
 # Fetch and compile the dependencies
 ARG MIX_ENV="prod"
+ARG GIT_SHA
 RUN mix deps.get --only ${MIX_ENV}
 RUN mix deps.compile --skip-umbrella-children
 
@@ -251,7 +251,9 @@ RUN cd apps/web \
     && mix assets.deploy
 
 # Copy the rest of the application files and compile them
-RUN mix compile
+# mix doesn't know when GIT_SHA changes, so --force is needed to avoid
+# pulling in a cached version.
+RUN mix compile --force
 
 FROM elixir AS builder
 
@@ -269,6 +271,7 @@ COPY rel rel
 
 ARG APPLICATION_NAME
 ARG MIX_ENV="prod"
+ARG GIT_SHA
 RUN mix release ${APPLICATION_NAME}
 
 # start a new build stage so that the final image will only contain
@@ -301,10 +304,6 @@ COPY --from=builder /app/_build/${MIX_ENV}/rel/${APPLICATION_NAME} ./
 # Allow the default user to write to the priv directory of some libraries
 RUN chmod -R ugo+rw /app/lib/tzdata-*/priv
 
-# Populate the SHA pointing to this build
-ARG GIT_SHA
-RUN echo ${GIT_SHA} > ./GIT_SHA
-
 # Change user to "default" to limit runtime privileges
 USER default
 

elixir/apps/api/mix.exs

@@ -2,11 +2,9 @@ defmodule API.MixProject do
   use Mix.Project
 
   def project do
-    {sha, _} = Code.eval_file(Path.join([__DIR__, "..", "..", "sha.exs"]))
-
     [
       app: :api,
-      version: "0.1.0+#{sha}",
+      version: version(),
       build_path: "../../_build",
       config_path: "../../config/config.exs",
       deps_path: "../../deps",
@@ -79,4 +77,9 @@ defmodule API.MixProject do
       test: ["ecto.create --quiet", "ecto.migrate", "test"]
     ]
   end
+
+  defp version do
+    sha = System.get_env("GIT_SHA", "deadbeef") |> String.trim()
+    "0.1.0+#{sha}"
+  end
 end

elixir/apps/domain/mix.exs

@@ -2,11 +2,9 @@ defmodule Domain.MixProject do
   use Mix.Project
 
   def project do
-    {sha, _} = Code.eval_file(Path.join([__DIR__, "..", "..", "sha.exs"]))
-
     [
       app: :domain,
-      version: "0.1.0+#{sha}",
+      version: version(),
       build_path: "../../_build",
       config_path: "../../config/config.exs",
       deps_path: "../../deps",
@@ -112,4 +110,9 @@ defmodule Domain.MixProject do
       test: ["ecto.create --quiet", "ecto.migrate", "test"]
     ]
   end
+
+  defp version do
+    sha = System.get_env("GIT_SHA", "deadbeef") |> String.trim()
+    "0.1.0+#{sha}"
+  end
 end

elixir/apps/web/mix.exs

@@ -2,11 +2,9 @@ defmodule Web.MixProject do
   use Mix.Project
 
   def project do
-    {sha, _} = Code.eval_file(Path.join([__DIR__, "..", "..", "sha.exs"]))
-
     [
       app: :web,
-      version: "0.1.0+#{sha}",
+      version: version(),
       build_path: "../../_build",
       config_path: "../../config/config.exs",
       deps_path: "../../deps",
@@ -104,4 +102,9 @@ defmodule Web.MixProject do
       test: ["ecto.create --quiet", "ecto.migrate", "test"]
     ]
   end
+
+  defp version do
+    sha = System.get_env("GIT_SHA", "deadbeef") |> String.trim()
+    "0.1.0+#{sha}"
+  end
 end

elixir/mix.exs

@@ -2,12 +2,10 @@ defmodule Firezone.MixProject do
   use Mix.Project
 
   def project do
-    {sha, _} = Code.eval_file(Path.join([__DIR__, "sha.exs"]))
-
     [
       name: :firezone,
       apps_path: "apps",
-      version: "0.1.0+#{sha}",
+      version: version(),
       start_permanent: Mix.env() == :prod,
       test_coverage: [tool: ExCoveralls],
       preferred_cli_env: [
@@ -95,4 +93,9 @@ defmodule Firezone.MixProject do
       ]
     ]
   end
+
+  defp version do
+    sha = System.get_env("GIT_SHA", "deadbeef") |> String.trim()
+    "0.1.0+#{sha}"
+  end
 end

elixir/sha.exs

@@ -1,7 +0,0 @@
-case File.read(Path.join([__DIR__, "GIT_SHA"])) do
-  {:ok, sha} ->
-    sha |> String.trim()
-
-  _ ->
-    "deadbeef"
-end