Adding gitspiegel-trigger workflow

[mutantcornholio]

Using a workflow to trigger mirroring instead of a webhook allows us to reuse "Approving workflow runs from public forks" GitHub feature to somewhat protect us from malicious PRs

[smiasojed]

@mutantcornholio, could you please elaborate a bit more on what 'Approving workflow runs from public forks' means? I assume you do not want to trigger GitLab workflows automatically. Currently, we are in the process of migrating from GitLab to GitHub Actions (GHA), so I assume that a similar approach should be implemented in GHA.

[mutantcornholio]

GitHub has a setting that requires manual click for executing GHA on the branch, for the first-time contributors: https://docs.github.com/en/actions/managing-workflow-runs/approving-workflow-runs-from-public-forks.

After this PR, gitspiegel will respect that setting.
So, for PRs from first-time contributors, gitspiegel won't do mirroring until the button in PR is clicked.
More info: https://github.com/paritytech/gitspiegel/issues/169

After you complete the migration to GHA, you can ask CICD team to stop mirroring project to gitlab, and remove this workflow as well.

[paritytech-cicd-pr]

🦑 📈 ink! Example Contracts ‒ Changes Report 📉 🦑

These are the results when building the integration-tests/* contracts from this branch with cargo-contract 4.0.0-alpha-e8c2cfc and comparing them to ink! master:

Contract	Upstream Size (kB)	PR Size (kB)	Diff (kB)	Diff (%)	Change
basic-contract-caller	2.967	2.967	0	0	➖
basic-contract-caller/other-contract	1.337	1.337	0	0	➖
call-builder-return-value	8.735	8.735	0	0	➖
call-runtime	1.769	1.769	0	0	➖
conditional-compilation	1.209	1.209	0	0	➖
contract-storage	7.171	7.171	0	0	➖
contract-terminate	1.092	1.092	0	0	➖
contract-transfer	1.444	1.444	0	0	➖
custom-allocator	7.428	7.428	0	0	➖
dns	7.249	7.249	0	0	➖
e2e-call-runtime	1.058	1.058	0	0	➖
e2e-runtime-only-backend	1.635	1.635	0	0	➖
erc1155	13.968	13.962	-0.006	-0.0429553	📉
erc20	6.687	6.687	0	0	➖
erc721	9.64	9.64	0	0	➖
events	4.763	4.763	0	0	➖
flipper	1.393	1.393	0	0	➖
incrementer	1.221	1.221	0	0	➖
lang-err-integration-tests/call-builder-delegate	2.317	2.317	0	0	➖
lang-err-integration-tests/call-builder	4.847	4.847	0	0	➖
lang-err-integration-tests/constructors-return-value	1.773	1.773	0	0	➖
lang-err-integration-tests/contract-ref	4.328	4.328	0	0	➖
lang-err-integration-tests/integration-flipper	1.571	1.571	0	0	➖
mapping-integration-tests	7.685	7.685	0	0	➖
mother	9.508	9.508	0	0	➖
multi-contract-caller	5.924	5.924	0	0	➖
multi-contract-caller/accumulator	1.095	1.095	0	0	➖
multi-contract-caller/adder	1.669	1.669	0	0	➖
multi-contract-caller/subber	1.689	1.689	0	0	➖
multisig	21.471	21.471	0	0	➖
payment-channel	5.501	5.501	0	0	➖
sr25519-verification	0.865	0.865	0	0	➖
static-buffer	1.405	1.405	0	0	➖
trait-dyn-cross-contract-calls	2.466	2.466	0	0	➖
trait-dyn-cross-contract-calls/contracts/incrementer	1.305	1.305	0	0	➖
trait-erc20	7.063	7.063	0	0	➖
trait-flipper	1.209	1.209	0	0	➖
trait-incrementer	1.37	1.37	0	0	➖
upgradeable-contracts/delegator	2.908	2.908	0	0	➖
upgradeable-contracts/delegator/delegatee	1.369	1.369	0	0	➖
upgradeable-contracts/set-code-hash	1.464	1.464	0	0	➖
upgradeable-contracts/set-code-hash/updated-incrementer	1.443	1.443	0	0	➖
wildcard-selector	2.622	2.622	0	0	➖

Link to the run | Last update: Mon Oct 30 12:03:13 CET 2023