Implements commands to recompute merge with git merge-file

extensions/git/src/commands.ts

@@ -1134,6 +1134,48 @@ export class CommandCenter {
 		}
 	}
 
+	@command('git.runGitMerge')
+	async runGitMergeNoDiff3(): Promise<void> {
+		await this.runGitMerge(false);
+	}
+
+	@command('git.runGitMergeDiff3')
+	async runGitMergeDiff3(): Promise<void> {
+		await this.runGitMerge(true);
+	}
+
+	private async runGitMerge(diff3: boolean): Promise<void> {
+		const { activeTab } = window.tabGroups.activeTabGroup;
+		if (!activeTab) {
+			return;
+		}
+
+		const input = activeTab.input as { base: Uri; input1: Uri; input2: Uri; result: Uri };
+
+		const result = await this.git.mergeFile({
+			basePath: input.base.fsPath,
+			input1Path: input.input1.fsPath,
+			input2Path: input.input2.fsPath,
+			diff3,
+		});
+
+		const doc = workspace.textDocuments.find(doc => doc.uri.toString() === input.result.toString());
+		if (!doc) {
+			return;
+		}
+		const e = new WorkspaceEdit();
+
+		e.replace(
+			input.result,
+			new Range(
+				new Position(0, 0),
+				new Position(doc.lineCount, 0),
+			),
+			result
+		);
+		await workspace.applyEdit(e);
+	}
+
 	private async _stageChanges(textEditor: TextEditor, changes: LineChange[]): Promise<void> {
 		const modifiedDocument = textEditor.document;
 		const modifiedUri = modifiedDocument.uri;

extensions/git/src/git.ts

@@ -656,6 +656,27 @@ export class Git {
 	private log(output: string): void {
 		this._onOutput.emit('log', output);
 	}
+
+	async mergeFile(options: { input1Path: string; input2Path: string; basePath: string; diff3?: boolean }): Promise<string> {
+		const args = ['merge-file', '-p', options.input1Path, options.basePath, options.input2Path];
+		if (options.diff3) {
+			args.push('--diff3');
+		} else {
+			args.push('--no-diff3');
+		}
+
+		try {
+			const result = await this.exec('', args);
+			return result.stdout;
+		} catch (err) {
+			if (typeof err.stdout === 'string') {
+				// The merge had conflicts, stdout still contains the merged result (with conflict markers)
+				return err.stdout;
+			} else {
+				throw err;
+			}
+		}
+	}
 }
 
 export interface Commit {