From ce5f4221e393d59d103553514e8be9ed7aeb1211 Mon Sep 17 00:00:00 2001
From: Cheng Liu <chengcyber@users.noreply.github.com>
Date: Wed, 29 May 2024 22:26:46 -0700
Subject: [PATCH 1/2] feat: support checkout -

---
 apps/sparo-lib/src/cli/commands/checkout.ts | 10 +++++-----
 apps/sparo-lib/src/services/GitService.ts   | 18 ++++++++++++++++++
 common/reviews/api/sparo-lib.api.md         |  1 +
 3 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/apps/sparo-lib/src/cli/commands/checkout.ts b/apps/sparo-lib/src/cli/commands/checkout.ts
index 4d50677..6a87d75 100644
--- a/apps/sparo-lib/src/cli/commands/checkout.ts
+++ b/apps/sparo-lib/src/cli/commands/checkout.ts
@@ -122,11 +122,11 @@ export class CheckoutCommand implements ICommand<ICheckoutCommandOptions> {
     if (!branch) {
       const checkoutIndex: number = process.argv.findIndex((value: string) => value === 'checkout');
       if (checkoutIndex >= 0 && process.argv[checkoutIndex + 1] === '-') {
-        branch = '-';
-        // FIXME: supports "sparo checkout -"
-        throw new Error(
-          `Git's "-" token is not yet supported. If this feature is important for your work, please let us know by creating a GitHub issue.`
-        );
+        // - is a shortcut of @{-1}
+        branch = gitService.getPreviousBranch(1);
+        if (!branch) {
+          throw new Error(`Argument "-" is unknown revision or path not in the working tree.`);
+        }
       }
     }
 
diff --git a/apps/sparo-lib/src/services/GitService.ts b/apps/sparo-lib/src/services/GitService.ts
index bf9e242..f7a52c0 100644
--- a/apps/sparo-lib/src/services/GitService.ts
+++ b/apps/sparo-lib/src/services/GitService.ts
@@ -445,6 +445,24 @@ Please specify a directory on the command line
     return currentBranch;
   }
 
+  /**
+   * Retrieves the previous branch name using `@{-n}` syntax
+   *
+   * Assume:
+   * git checkout feature
+   * git checkout main
+   * ---
+   * `git checkout @{-1}` equals to run `git checkout feature`.
+   * Running `getPreviousBranch(1)` works in the similar way and returns "feature" in this case.
+   */
+  public getPreviousBranch(n: number): string {
+    const result: string = this.executeGitCommandAndCaptureOutput({
+      args: ['rev-parse', '--symbolic-full-name', '--abbrev-ref=loose', `@{-${n}}`]
+    }).trim();
+    this._terminalService.terminal.writeDebugLine(`getPreviousBranch ${n}: ${result}`);
+    return result;
+  }
+
   /**
    * Check existence for a list of branch name
    */
diff --git a/common/reviews/api/sparo-lib.api.md b/common/reviews/api/sparo-lib.api.md
index 7a28d3c..18ee7e6 100644
--- a/common/reviews/api/sparo-lib.api.md
+++ b/common/reviews/api/sparo-lib.api.md
@@ -46,6 +46,7 @@ export class GitService {
     getIsSparseCheckoutMode(): boolean | undefined;
     // (undocumented)
     getObjectType(object: string): IObjectType | undefined;
+    getPreviousBranch(n: number): string;
     // (undocumented)
     getRepoInfo(): GitRepoInfo;
     get gitPath(): string | undefined;

From 7ea9bdcdde23c4b390e92a78c868f9ea6835ee79 Mon Sep 17 00:00:00 2001
From: Cheng Liu <chengcyber@users.noreply.github.com>
Date: Wed, 29 May 2024 22:28:41 -0700
Subject: [PATCH 2/2] chore: rush change

---
 .../sparo/feat-checkout-dash_2024-05-30-05-28.json     | 10 ++++++++++
 1 file changed, 10 insertions(+)
 create mode 100644 common/changes/sparo/feat-checkout-dash_2024-05-30-05-28.json

diff --git a/common/changes/sparo/feat-checkout-dash_2024-05-30-05-28.json b/common/changes/sparo/feat-checkout-dash_2024-05-30-05-28.json
new file mode 100644
index 0000000..1e87e08
--- /dev/null
+++ b/common/changes/sparo/feat-checkout-dash_2024-05-30-05-28.json
@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "sparo",
+      "comment": "\"sparo checkout -\" can checkout to previous branch correctly",
+      "type": "none"
+    }
+  ],
+  "packageName": "sparo"
+}
\ No newline at end of file