Update latexdiff.yml

fix  Alpine’s “externally‐managed‐environment” restriction by install flatex inside a virtual environment rather than system‐wide

.github/workflows/latexdiff.yml

@@ -17,7 +17,7 @@ jobs:
     runs-on: ubuntu-latest
     container:
       image: ghcr.io/xu-cheng/texlive-full:latest
-      options: --user root  # allow package install if needed
+      options: --user root
 
     steps:
       - name: Checkout base branch
@@ -32,23 +32,25 @@ jobs:
           ref: ${{ github.event.inputs.compare_branch }}
           path: compare
 
-      - name: Install flatex (Python flattener)
+      - name: Install flatex (in a virtualenv)
         run: |
-          apk add --no-cache py3-pip  # if Alpine base
+          python3 -m venv /tmp/latex-venv
+          . /tmp/latex-venv/bin/activate
           pip install flatex
+          ln -s /tmp/latex-venv/bin/flatex /usr/local/bin/flatex
 
       - name: Create output folder
         run: mkdir -p diff_output
 
-      - name: Flatten base branch
+      - name: Flatten base/main.tex
         run: |
           flatex base/latex/main.tex > diff_output/base_flat.tex
 
-      - name: Flatten compare branch
+      - name: Flatten compare/main.tex
         run: |
           flatex compare/latex/main.tex > diff_output/compare_flat.tex
 
-      - name: Generate diff.tex using latexdiff
+      - name: Generate diff.tex
         run: |
           latexdiff diff_output/base_flat.tex diff_output/compare_flat.tex > diff_output/diff.tex
 
@@ -63,3 +65,4 @@ jobs:
         with:
           name: latex-diff-output
           path: diff_output/
+