Add README.md, add more tests, minor tweaks to behaviour to match desired test output

Author: AbitTheGray

.github/workflows/main.yml

@@ -1,9 +1,56 @@
 on: [push]
 
 jobs:
-  plugin_json:
+  empty_data:
     runs-on: ubuntu-latest
-    name: Test merging some JSON files
+    name: Test for no output file with no input data
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Test
+        uses: ./
+        with:
+          out-file: output.json
+
+      - name: xxx
+        shell: bash
+        run: |
+          if [ -f 'output.json' ]; then
+            echo "There is still an output file, this is incorrect"
+            exit 1
+          else
+            echo "No output file"
+          fi
+  file_to_file:
+    runs-on: ubuntu-latest
+    name: Test just copying the file
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Test
+        uses: ./
+        with:
+          in-file: test/file.json
+          out-file: output_single.json
+
+      - name: Print output
+        shell: bash
+        run: |
+          wc -c < output_single.json
+          cat output_single.json
+          echo
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: output
+          path: output_single.json
+
+  json_merging:
+    runs-on: ubuntu-latest
+    name: Test merging logic
     steps:
       - name: Checkout
         uses: actions/checkout@v4

README.md

@@ -0,0 +1,38 @@
+# Voxelite JSON Merger
+
+GitHub Action to merge [Voxelite](https://github.com/voxelite)'s `block.json` (main JSON) with all JSONs in `block` directory.
+The same can be done for items, entities...
+
+## Inputs
+
+### `in-file`
+
+Path to your `block.json` (or equivalent).
+
+This is your main file with data.
+Inside the file you should have a JSON Object with keys for codenames and their values an object with all the configuration.
+
+### `in-directory`
+
+Path to your directory containing all object files.
+Inside each object (like a block) is represented by a single JSON file.
+Name of the file is used as the object's name and inside is a JSON Object with all the configuration.
+
+### `out-file`
+
+**Required**
+
+File to write the output JSON into.
+
+## Example usage
+
+```yaml
+- name: block.json merging
+  uses: voxelite/json-merge@v1
+  with:
+    in-file: block.json
+    in-directory: block
+    out-file: out_block.json
+```
+
+For object format (block, item, entity...) look into official documentation.

index.js

@@ -14,13 +14,13 @@ try
 
     let outputJson = JSON.constructor();
 
-    if(inFile !== undefined)
+    if(typeof inFile === "string" && inFile !== '')
     {
         const fileData = fs.readFileSync(inFile, 'utf8');
         outputJson = JSON.parse(fileData);
     }
 
-    if(inDirectory !== undefined)
+    if(typeof inDirectory === "string" && inDirectory !== '')
     {
         fs.readdirSync(inDirectory).forEach(filename => {
             if(!filename.endsWith(".json"))
@@ -38,6 +38,7 @@ try
         });
     }
 
+    if(outputJson.length > 0)
     {
         fs.writeFileSync(
             outFile,