feat(github): Add basic templating support for Github Actions

src/template.rs

@@ -1,6 +1,6 @@
 use std::{
     collections::HashMap,
-    fs,
+    env, fs,
     path::{Path, PathBuf},
     process,
 };
@@ -164,6 +164,16 @@ impl TemplateCommand {
             },
         );
 
+        debug!("Registering function `running_gitlab_actions`");
+        tera.register_function(
+            "running_gitlab_actions",
+            |_: &HashMap<String, tera::Value>| -> tera::Result<tera::Value> {
+                trace!("tera fn running_gitlab_actions()");
+
+                Ok(env::var("GITHUB_ACTIONS").is_ok_and(|e| e == "true").into())
+            },
+        );
+
         Ok((tera, context))
     }
 }

templates/Containerfile.tera

@@ -1,6 +1,10 @@
 FROM {{ base_image }}:{{ image_version }}
 
 ARG RECIPE={{ recipe }}
+{%- if running_gitlab_actions() %}
+ARG IMAGE_REGISTRY=ghcr.io/ublue-os
+COPY cosign.pub /usr/share/ublue-os/cosign.pub
+{%- endif %}
 
 # Copy the bling from ublue-os/bling into tmp, to be installed later by the bling module
 # Feel free to remove these lines if you want to speed up image builds and don't want any bling