docs: python flask gitops use case with tools

Signed-off-by: Tiexin Guo <[email protected]>

Author: IronCore864

docs/use-cases/gitops-python-flask/2-github-dtm-apps.md

@@ -22,7 +22,7 @@ config:
 
 vars:
   GITHUB_USER: YOUR_GITHUB_USER
-  DOCKERHUB_USER: YOUR_DOCKERHUB_USER    
+  DOCKERHUB_USER: YOUR_DOCKERHUB_USER
 
 tools:
 - name: helm-installer

docs/use-cases/gitops-python-flask/3-github-dtm-tools.md

@@ -1,3 +1,89 @@
 # GitHub + GitHub Actions with DTM Tools
 
-TODO
+DevStream has two abstractions: [Tools](../../core-concepts/tools.md) and [Apps](../../core-concepts/apps.md).
+
+[The previous use case](./2-github-dtm-apps.md) uses "Apps". We can also achieve the same result with "Tools", and here's how:
+
+---
+
+## Config File
+
+```yaml
+config:
+  state:
+    backend: local
+    options:
+      stateFile: devstream.state
+
+vars:
+  GITHUB_USER: YOUR_GITHUB_USER
+  DOCKERHUB_USER: YOUR_DOCKERHUB_USER
+
+tools:
+- name: repo-scaffolding
+  instanceID: myapp1
+  options:
+    destinationRepo:
+      owner: [[ GITHUB_USER ]]
+      name: myapp1
+      branch: main
+      scmType: github
+    sourceRepo:
+      org: devstream-io
+      name: dtm-repo-scaffolding-python-flask
+      scmType: github
+- name: github-actions
+  instanceID: flask
+  dependsOn: [ repo-scaffolding.myapp1 ]
+  options:
+    scm:
+      owner: [[ GITHUB_USER ]]
+      name:  myapp1
+      scmType: github
+    pipeline:
+      configLocation: https://raw.githubusercontent.com/devstream-io/dtm-pipeline-templates/main/github-actions/workflows/main.yml
+      language:
+        name: python
+        framework: flask
+      imageRepo:
+        user: [[ DOCKERHUB_USER ]]
+- name: helm-installer
+  instanceID: argocd
+- name: argocdapp
+  instanceID: default
+  dependsOn: [ "helm-installer.argocd", "github-actions.flask" ]
+  options:
+    app:
+      name: myapp1
+      namespace: argocd
+    destination:
+      server: https://kubernetes.default.svc
+      namespace: default
+    source:
+      valuefile: values.yaml
+      path: helm/myapp1
+      repoURL: ${{repo-scaffolding.myapp1.outputs.repoURL}}
+    imageRepo:
+      user: [[ DOCKERHUB_USER ]]
+```
+
+Update the "YOUR_GITHUB_USER" and "YOUR_DOCKERHUB_USER" in the above file accordingly.
+
+---
+
+## Run
+
+First, initialize:
+
+```bash
+# this downloads the required plugins, according to the config file, automatically.
+dtm init -f config.yaml
+```
+
+Then we apply it by running:
+
+```bash
+dtm apply -f config.yaml -y
+```
+
+(Screenshot/video omitted.)