Fix README.md

README.md

@@ -436,14 +436,69 @@ stages:
 
 Every job that will use the Terraform configuration file needs to copy
 the file referred by `SSH_PRIVATE_KEY` into the file `id_rsa`.
-To copy the file without overriding all the script,
-we use the `before_script` key:
-defining the `before_script` key at top-level, outside any job,
-makes the file be copied before every job.
+To copy the file without overriding the script inherited from the
+Terraform template, we use the `before_script` key:
+we define a template job `.with-rsa-key`, which every job requiring
+the `id_rsa` file will extend
+(if there were no `execute` jobs, we could also have defined the
+`before_script` key at top-level, outside any job,
+making the file be copied before every job).
 
 ```yaml
-before_script:
-  - cp $SSH_PRIVATE_KEY id_rsa
+.with-rsa-key:
+  before_script:
+    - cp $SSH_PRIVATE_KEY id_rsa
+```
+
+By default, the `deploy` job is defined as manual in the template.
+To execute it automatically, we redefine the `rules:` key as empty.
+
+```yaml
+deploy:
+  tags:
+    - linux
+    - small
+  extends:
+    - .terraform:deploy
+    - .with-rsa-key
+  dependencies:
+    - build
+  rules:
+```
+
+In the `execute` stage, we compile `hello_world.c` with `gcc`
+on Ubuntu, `cl` (Microsoft Visual Studio) on Windows,
+and `clang` on Mac OS X.
+On Windows, we need to run `vcvars64.bat` to get the
+environment initialized for Visual Studio.
+This batch file requires CMD shell, whereas `gitlab-runner`
+deprecates CMD in favor of PowerShell (see
+[documentation](https://docs.gitlab.com/runner/shells/)).
+The documentation gives the following
+[trick](https://gitlab.com/guided-explorations/microsoft/windows/call-cmd-from-powershell/-/blob/master/.gitlab-ci.yml) to execute batch files with CMD from PowerShell:
+write the script in a file and run `CMD.EXE /C` on it.
+
+```yaml
+execute windows:
+  stage: execute
+  image: alpine
+  tags:
+    - terraform
+    - windows
+  script:
+    # The trick for running cmd scripts from powershell runner is documented
+    # here:
+    # https://gitlab.com/guided-explorations/microsoft/windows/call-cmd-from-powershell/-/blob/master/.gitlab-ci.yml
+    - |
+      set-content $env:public\inline.cmd -Value @'
+      call "C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Auxiliary\Build\vcvars64.bat"
+      cl /Fe:hello_world.exe hello_world.c
+      '@
+      CMD.EXE /C $env:public\inline.cmd
+      exit $LASTEXITCODE
+  artifacts:
+    paths:
+      - hello_world.exe
 ```
 
 ## Ignored files in [`.gitignore`](.gitignore)