Fix P4Merge text argument order

docs/diff-tool.md

@@ -716,11 +716,11 @@ DiffTools.UseOrder(DiffTool.P4Merge);
 
   * Example target on left arguments for text:
    ```
-   -C utf8-bom "tempFile.txt" "targetFile.txt"
+   -C utf8-bom "targetFile.txt" "tempFile.txt"
    ```
   * Example target on right arguments for text:
    ```
-   -C utf8-bom "targetFile.txt" "tempFile.txt"
+   -C utf8-bom "tempFile.txt" "targetFile.txt"
    ```
   * Example target on left arguments for binary:
    ```
@@ -740,11 +740,11 @@ DiffTools.UseOrder(DiffTool.P4Merge);
 
   * Example target on left arguments for text:
    ```
-   -C utf8-bom "tempFile.txt" "targetFile.txt"
+   -C utf8-bom "targetFile.txt" "tempFile.txt"
    ```
   * Example target on right arguments for text:
    ```
-   -C utf8-bom "targetFile.txt" "tempFile.txt"
+   -C utf8-bom "tempFile.txt" "targetFile.txt"
    ```
   * Example target on left arguments for binary:
    ```
@@ -762,11 +762,11 @@ DiffTools.UseOrder(DiffTool.P4Merge);
 
   * Example target on left arguments for text:
    ```
-   -C utf8-bom "tempFile.txt" "targetFile.txt"
+   -C utf8-bom "targetFile.txt" "tempFile.txt"
    ```
   * Example target on right arguments for text:
    ```
-   -C utf8-bom "targetFile.txt" "tempFile.txt"
+   -C utf8-bom "tempFile.txt" "targetFile.txt"
    ```
   * Example target on left arguments for binary:
    ```

src/DiffEngine.Tests/diffTools.include.md

@@ -581,11 +581,11 @@ DiffTools.UseOrder(DiffTool.P4Merge);
 
   * Example target on left arguments for text:
    ```
-   -C utf8-bom "tempFile.txt" "targetFile.txt"
+   -C utf8-bom "targetFile.txt" "tempFile.txt"
    ```
   * Example target on right arguments for text:
    ```
-   -C utf8-bom "targetFile.txt" "tempFile.txt"
+   -C utf8-bom "tempFile.txt" "targetFile.txt"
    ```
   * Example target on left arguments for binary:
    ```
@@ -605,11 +605,11 @@ DiffTools.UseOrder(DiffTool.P4Merge);
 
   * Example target on left arguments for text:
    ```
-   -C utf8-bom "tempFile.txt" "targetFile.txt"
+   -C utf8-bom "targetFile.txt" "tempFile.txt"
    ```
   * Example target on right arguments for text:
    ```
-   -C utf8-bom "targetFile.txt" "tempFile.txt"
+   -C utf8-bom "tempFile.txt" "targetFile.txt"
    ```
   * Example target on left arguments for binary:
    ```
@@ -627,11 +627,11 @@ DiffTools.UseOrder(DiffTool.P4Merge);
 
   * Example target on left arguments for text:
    ```
-   -C utf8-bom "tempFile.txt" "targetFile.txt"
+   -C utf8-bom "targetFile.txt" "tempFile.txt"
    ```
   * Example target on right arguments for text:
    ```
-   -C utf8-bom "targetFile.txt" "tempFile.txt"
+   -C utf8-bom "tempFile.txt" "targetFile.txt"
    ```
   * Example target on left arguments for binary:
    ```

src/DiffEngine/Implementation/P4Merge.cs

@@ -3,11 +3,14 @@ static partial class Implementation
     public static Definition P4Merge()
     {
         var launchArguments = new LaunchArguments(
+            // p4merge takes the two files positionally as `left right`, so the target leads for
+            // target-on-left and the temp file leads for target-on-right. Same order for text and
+            // binary; only the encoding switch differs.
             Left: (temp, target) =>
             {
                 if (FileExtensions.IsTextFile(temp))
                 {
-                    return $"-C utf8-bom \"{temp}\" \"{target}\"";
+                    return $"-C utf8-bom \"{target}\" \"{temp}\"";
                 }
 
                 return $"\"{target}\" \"{temp}\"";
@@ -16,7 +19,7 @@ public static Definition P4Merge()
             {
                 if (FileExtensions.IsTextFile(temp))
                 {
-                    return $"-C utf8-bom \"{target}\" \"{temp}\"";
+                    return $"-C utf8-bom \"{temp}\" \"{target}\"";
                 }
 
                 return $"\"{temp}\" \"{target}\"";