Reworks commanding structure for less redundancy

Adds command args copying when needed

src/commands/diffWithPrevious.ts

@@ -1,7 +1,7 @@
 'use strict';
 import { Iterables } from '../system';
 import { commands, Range, TextDocumentShowOptions, TextEditor, Uri, window } from 'vscode';
-import { ActiveEditorCommand, CommandContext, Commands, getCommandUri } from './common';
+import { ActiveEditorCommand, Commands, getCommandUri } from './common';
 import { BuiltInCommands, GlyphChars } from '../constants';
 import { DiffWithWorkingCommandArgs } from './diffWithWorking';
 import { GitCommit, GitService, GitUri } from '../gitService';
@@ -22,25 +22,11 @@ export class DiffWithPreviousCommand extends ActiveEditorCommand {
         super(Commands.DiffWithPrevious);
     }
 
-    async run(context: CommandContext, args: DiffWithPreviousCommandArgs = {}): Promise<any> {
-        // Since we can change the args and they could be cached -- make a copy
-        switch (context.type) {
-            case 'uri':
-                return this.execute(context.editor, context.uri, { ...args });
-            case 'scm-states':
-                const resource = context.scmResourceStates[0];
-                return this.execute(undefined, resource.resourceUri, { ...args });
-            case 'scm-groups':
-                return undefined;
-            default:
-                return this.execute(context.editor, undefined, { ...args });
-        }
-    }
-
-    async execute(editor: TextEditor | undefined, uri?: Uri, args: DiffWithPreviousCommandArgs = {}): Promise<any> {
+    async execute(editor?: TextEditor, uri?: Uri, args: DiffWithPreviousCommandArgs = {}): Promise<any> {
         uri = getCommandUri(uri, editor);
         if (uri === undefined) return undefined;
 
+        args = { ...args };
         if (args.line === undefined) {
             args.line = editor === undefined ? 0 : editor.selection.active.line;
         }