ci(workflows): enhance debug logging and safety in image detection

Refactor the 'Detect changed images' step in the build-images workflow to improve robustness and debuggability.

Changes include:
- Pass `inputs.image` via an environment variable (`INPUT_IMAGE`) to avoid potential injection issues or syntax errors in shell scripts.
- Add comprehensive `DEBUG` echo statements to trace the logic flow for both manual and automatic detection paths.
- Use `printf` instead of `echo` for writing to `$GITHUB_OUTPUT` to ensure safer handling of string outputs.
- Remove redundant comments to clean up the script block.

.gitea/workflows/build-images.yml

@@ -36,16 +36,22 @@ jobs:
 
       - name: Detect changed images
         id: changes
+        env:
+          INPUT_IMAGE: ${{ inputs.image }}
         run: |
           # 1. Handle Manual Input
-          if [ -n "${{ inputs.image }}" ]; then
+          if [ -n "$INPUT_IMAGE" ]; then
             # Clean input
-            IMAGE=$(echo "${{ inputs.image }}" | xargs)
+            IMAGE=$(echo "$INPUT_IMAGE" | xargs)
+            echo "DEBUG: Processing manual input image: '$IMAGE'"
+            
             if [ -n "$IMAGE" ]; then
               if [ -d "images/$IMAGE" ] && [ -f "images/$IMAGE/Dockerfile" ]; then
-                 echo "Manual image detected: $IMAGE"
+                 echo "DEBUG: Image directory and Dockerfile exist."
-                 echo "matrix=[\"$IMAGE\"]" >> $GITHUB_OUTPUT
+                 # Use printf for safer output
+                 printf "matrix=[\"%s\"]\n" "$IMAGE" >> $GITHUB_OUTPUT
                  echo "has_changes=true" >> $GITHUB_OUTPUT
+                 echo "DEBUG: Set matrix=['$IMAGE']"
                  exit 0
               else
                  echo "Error: Image '$IMAGE' not found or missing Dockerfile at images/$IMAGE/Dockerfile"
@@ -54,7 +60,7 @@ jobs:
                  exit 0
               fi
             else
-               echo "Input image name was empty."
+               echo "DEBUG: Input image name was empty after trimming."
                echo "has_changes=false" >> $GITHUB_OUTPUT
                echo "matrix=[]" >> $GITHUB_OUTPUT
                exit 0
@@ -62,15 +68,14 @@ jobs:
           fi
 
           # 2. Handle Automatic Detection (Git Diff)
+          echo "DEBUG: Running git diff detection..."
           > valid_images.txt
           
           CHANGED_FILES=$(git diff --name-only HEAD~1 HEAD -- images/ 2>/dev/null || true)
           
-          # Extract potential image directories (first level subdirs in images/)
           CANDIDATES=$(echo "$CHANGED_FILES" | cut -d'/' -f2 | sort -u | grep -v '^$')
           
           for CANDIDATE in $CANDIDATES; do
-            # Verify it's a directory with a Dockerfile
             if [ -d "images/$CANDIDATE" ] && [ -f "images/$CANDIDATE/Dockerfile" ]; then
               echo "$CANDIDATE" >> valid_images.txt
             fi