[llvm] add logging to pipeline generation (PR #68983)

[Mikhail Goncharov via llvm-commits]

https://github.com/metaflow created https://github.com/llvm/llvm-project/pull/68983

we tried to generate a full diff against main in
ec9d80ec43f5761a34c4a785c67d9e7d21ec8bda but it resulted in wrong diffs [citation needed]. Trying to debug this by adding logs.

>From 31ad9c9bf1f5df67e1e33573237fafb67eff23f5 Mon Sep 17 00:00:00 2001
From: Mikhail Goncharov <goncharov.mikhail at gmail.com>
Date: Fri, 13 Oct 2023 14:19:59 +0200
Subject: [PATCH] add logging to pipeline generation

we tried to generate a full diff against main in
ec9d80ec43f5761a34c4a785c67d9e7d21ec8bda but it resulted in wrong diffs
[citation needed]. Trying to debug this by adding logs.
---
 .ci/generate-buildkite-pipeline-premerge | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/.ci/generate-buildkite-pipeline-premerge b/.ci/generate-buildkite-pipeline-premerge
index e389df431505bd1..9e69ab0e194f190 100755
--- a/.ci/generate-buildkite-pipeline-premerge
+++ b/.ci/generate-buildkite-pipeline-premerge
@@ -23,6 +23,15 @@ set -o pipefail
 # Environment variables script works with:
 # List of files affected by this commit
 : ${MODIFIED_FILES:=$(git diff --name-only HEAD~1)}
+echo "files modified HEAD~1" >&2
+git diff --name-only HEAD~1 >&2
+echo "files modified main..." >&2
+git diff --name-only main...HEAD >&2
+echo "files modified origin/main..." >&2
+git diff --name-only origin/main...HEAD >&2
+merge_base=$(git merge-base main HEAD)
+echo "merge base with main $merge_base" >&2
+git diff --name-only "$merge_base"..HEAD >&2
 # Filter rules for generic windows tests
 : ${WINDOWS_AGENTS:='{"queue": "windows"}'}
 # Filter rules for generic linux tests