feat: implement sapling source control provider

Summary:

You can now use conventional tools in a sapling repo (maybe).

Test Plan:

This has not really been tested yet, but the code is there. This is very much a
WIP, the users will be using this at their own risk.

src/lib/source-control/index.ts

@@ -1,4 +1,5 @@
 import git from './git';
+import sapling from './sapling';
 
 export interface SourceControlProvider {
   /**
@@ -11,9 +12,13 @@ export interface SourceControlProvider {
    * are not currently on one.
    */
   getBranchName(): Promise<string | null>;
+  /**
+   * Get the current root directory of for the repository.
+   */
+  root(): Promise<string>;
 }
 
-const PROVIDERS = [git];
+const PROVIDERS = [git, sapling];
 
 export async function getSourceControlProvider(): Promise<
   SourceControlProvider | undefined

src/lib/source-control/sapling.ts

@@ -0,0 +1,25 @@
+import {run} from '../exec';
+import type {SourceControlProvider} from '.';
+
+const sapling: SourceControlProvider = {
+  isEnabled: async () => {
+    const isSapling = await run(`sl root`);
+    return isSapling.code === 0;
+  },
+
+  getBranchName: async () => {
+    const {stdout} = await run(`sl log -r '.' -T"{bookmarks}"`);
+    if (!stdout.trim()) {
+      return null;
+    }
+
+    return stdout.trim();
+  },
+
+  root: async () => {
+    const {stdout} = await run(`sl root`);
+    return stdout.trim();
+  },
+};
+
+export default sapling;

tests/commands/commitgen.spec.ts

@@ -28,6 +28,7 @@ describe('command/commitgen', () => {
         async () => ({
           isEnabled: async () => true,
           getBranchName: async () => `${type}/123`,
+          root: async () => '/',
         }),
       );
 
@@ -79,6 +80,7 @@ describe('command/commitgen', () => {
         async () => ({
           isEnabled: async () => true,
           getBranchName: async () => `feat/123`,
+          root: async () => '/',
         }),
       );