Merge branch 'sync' of https://github.com/gitgitgadget/git-mailing-list-mirror

The main aim is to pull the workflow that keeps that mirror up to date
into the `gitgitgadget-workflows` org, so that the concurrency limits of
the `gitgitgadget` org (which the "interesting" practice of frequently
pushing gazillions of branches at the same time stresses it to its
seams) cannot prevent the mailing list mirror from being updated.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.github/workflows/sync.yml

@@ -0,0 +1,31 @@
+name: sync
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron:  "2,7,12,17,22,27,32,37,42,47,52,57 * * * *"
+  push:
+    branches: [ sync ]
+
+env:
+  LORE_EPOCH: 1
+
+concurrency: sync
+
+jobs:
+  repo-sync:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+    - name: Partial clone
+      run: |
+        git clone --bare --depth=1 -b lore-$LORE_EPOCH --filter=blob:none https://github.com/$GITHUB_REPOSITORY .
+    - name: Update from lore.kernel.org
+      run: |
+        git fetch https://lore.kernel.org/git/$LORE_EPOCH refs/heads/master:refs/heads/lore-$LORE_EPOCH
+    - name: Push to mirror
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      run: |
+        git push https://$GITHUB_ACTOR:$GITHUB_TOKEN@github.com/$GITHUB_REPOSITORY lore-$LORE_EPOCH

README.md

@@ -1 +1,9 @@
-# workflow-runner
+# GitGitGadget workflows
+
+This repository contains GitHub workflows, i.e. automated tasks, that keep [GitGitGadget](https://gitgitgadget.github.io/) running.
+
+## Keeping the mirror of the Git mailing list up to date
+
+The `sync-git-mailing-list.yml` workflow keeps the mirror at https://github.com/gitgitgadget/git-mailing-list of the Git mailing list mirror at https://lore.kernel.org/git up to date. Since that mirror chunks the archive by epochs, this mirror fetches each epoch into its own branch: the oldest epoch into `lore-0`, the next one into `lore-1`, etc.
+
+Previously, this workflow lived in the `git-mailing-list` repository in the `sync` branch, which was the default branch because scheduled workflows _must_ live in the default branch.