[llvm] [Github] Only look at previous commit for MacOS Premerge (PR #164483)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 created https://github.com/llvm/llvm-project/pull/164483

Otherwise we're looking for a commit that does not exist given the fetch depth.

Fixes #164430.

>From b3f5381df5a9cf0af3dd042f8d9bdfb27d0e9926 Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman at google.com>
Date: Tue, 21 Oct 2025 19:50:52 +0000
Subject: [PATCH] [Github] Only look at previous commit for MacOS Premerge

Otherwise we're looking for a commit that does not exist given the fetch
depth.

Fixes #164430.
---
 .github/workflows/premerge.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/premerge.yaml b/.github/workflows/premerge.yaml
index 951fc16bed215..6303a119750b5 100644
--- a/.github/workflows/premerge.yaml
+++ b/.github/workflows/premerge.yaml
@@ -193,7 +193,7 @@ jobs:
         uses: llvm/actions/install-ninja at main
       - name: Build and Test
         run: |
-          source <(git diff --name-only HEAD~2..HEAD | python3 .ci/compute_projects.py)
+          source <(git diff --name-only HEAD~1...HEAD | python3 .ci/compute_projects.py)
 
           if [[ "${projects_to_build}" == "" ]]; then
             echo "No projects to build"