ci: auto backport squashed commits based on labels

[ankush]

Workflow to auto backport squashed PR merges.

Use this label scheme for creating backports: backport <branchname>

Example : backport version-13-hotfix

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Credit:

This is based on work of https://github.com/tibdex/backport with subsequent modification from https://github.com/grafana/grafana-github-actions (which in turn is based on https://github.com/microsoft/vscode-github-triage-actions)

All repos are licensed under MIT License.

[ankush]

will move the workflow action to frappe org once it's stable.

[frappe-pr-bot]

The backport to version-12-hotfix failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new branch
git switch --create backport/version-12-hotfix/26622 origin/version-12-hotfix
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x 057a0a98428b138b20646b820e7ab27c99bc5f22
# Push it to GitHub
git push --set-upstream origin backport/version-12-hotfix/26622
git switch main
# Remove the local backport branch
git branch -D backport/version-12-hotfix/26622

Then, create a pull request where the base branch is version-12-hotfix and the compare/head branch is backport/version-12-hotfix/26622.