[Workflow] Add Release Repo sync script

[thieta]

Summary

Adds a bash script that syncs llvm/llvm-project and llvm/llvm-project-release-prs.
This should run on pushes to any of the repositories release branches.

I will follow this up with a change to the github actions to run this
script.

This breaks out the sync script from: https://reviews.llvm.org/D133476
so we can keep them separate.

[thieta]

ping on this @tstellar / @kwk

[kwk]

@thieta I hope my comments make some sense.

llvm/utils/git/sync-release-repo.sh

6

Does it make sense to check for this origin?

17

If you default to some "random" UUID you don't have to worry about a remote already exsting.

Oh, and since we're at it. Could you explain a bit what origin is for you and what upstream?

42–43

The text says "pushing to origin" but you're pushing to "upstream" is that on purpose? Sorry it is late here and I might not follow everything.

46–53

I'm not sure this should be done. I mean afterall this script is called from a github action and why do you care how the state of that repo looks like? All cleanup steps can be removed IMHO

[thieta]

• Generate remote and branch names
• Make terminology a lot clearer
• Make cleanup optional

[thieta]

In D142726#4111037, @kwk wrote:

@thieta I hope my comments make some sense.

Your comments made total sense, it was hard to follow the different names, I cleaned it up and hopefully it's much easier to follow now. Plus added uuidgen (thanks for that tip!) to generate remotes and branch names.

The cleanup is there to make it easier to debug locally, especially now with the generated names. But I put them in a block for debug, hope that's fine!

[kwk]

llvm/utils/git/sync-release-repo.sh

21–27

You're only using the remote URLs once so no need for the variable.

I've re-added the CURRENT_BRANCH in order for the cleanup to go back where you came from.

44

56–57

65

One not necessarily was on the main branch.

[thieta]

Incorporated feedback

[thieta]

Thanks for your suggestions. I have pushed a new diff with the fixes.

[thieta]

Fix comment

[kwk]

LGTM except for a more detailed explanation in the comments at one place and except for a small change that slipped in because I requested too many changes ;)

llvm/utils/git/sync-release-repo.sh

16–17

Sorry to be nitpicking, but the $MAIN_URL and $REMOTE_URL variables no longer exist, Just add the llvm/llvm-project and llvm/llvm-project-release-prs repo references here is probably enough.

45

It would be nice to understand through the comment here what magic happens and why we need to update again before we can continue with the merge below.

[thieta]

Expanded and fixed comments

[thieta]

Thanks for your review @kwk - I'll merge this now and start working on the action trigger.

llvm/utils/git/sync-release-repo.sh

+#!/bin/bash
+
+# This script will sync github.com/llvm/llvm-project with
+# github.com/llvm/llvm-project-release-prs and try to merge
+# the changes in the release branch.
+
+set -e
+set -x
+
+# We should always get the branch from the environment.
+# But otherwise just default to something. We can probably
+# have a better default here?
+RELEASE_BRANCH="${RELEASE_BRANCH:-release/16.x}"
+
+# We will add two remotes here:
+#  main - which will point to $MAIN_URL
+#  release - which will point to $RELEASE_URL
+# The remotes will use random strings to avoid
+# collisions
+MAIN_REMOTE=$(uuidgen)
+RELEASE_REMOTE=$(uuidgen)
+CURRENT_BRANCH=$(git rev-parse --abbrev-ref HEAD)
+
+git remote add $MAIN_REMOTE "https://github.com/llvm/llvm-project"
+git remote add $RELEASE_REMOTE "https://github.com/llvm/llvm-project-release-prs"
+
+# Make sure we are up to date on all our repos first
+git fetch $MAIN_REMOTE
+git fetch $RELEASE_REMOTE
+
+# Create our sync branch. Starting with the main
+# repo first since it's important to get those
+# changes
+MERGE_BRANCH=$(uuidgen)
+git switch -c $MERGE_BRANCH $MAIN_REMOTE/$RELEASE_BRANCH
+
+# Merge changes from the release repo
+git merge --ff-only $RELEASE_REMOTE/$RELEASE_BRANCH
+
+if ! git diff-index --quiet $MAIN_REMOTE/$RELEASE_BRANCH; then
+  echo "Changes in the release remote - pushing to main remote"
+  git push $MAIN_REMOTE $MERGE_BRANCH:$RELEASE_BRANCH
+fi
+
+# Then we need to update again
+git fetch $MAIN_REMOTE
+git fetch $RELEASE_REMOTE
+
+# And merge all the new data to the current branch
+git merge --ff-only $MAIN_REMOTE/$RELEASE_BRANCH
+
+# If anything changed let's merge it
+if ! git diff-index --quiet $RELEASE_REMOTE/$RELEASE_BRANCH; then
+  echo "Changes in main - pushing to release"
+  git push $RELEASE_REMOTE $MERGE_BRANCH:$RELEASE_BRANCH
+fi
+
+# Cleanup - enable for debug
+if false; then
+  git remote remove $RELEASE_REMOTE
+  git remote remove $MAIN_REMOTE
+
+  git switch $CURRENT_BRANCH
+  git branch -D $MERGE_BRANCH
+fi