Merge pull request 'chore(deps): update woodpeckerci/plugin-docker-buildx docker tag to v6' (#8) from renovate/woodpeckerci-plugin-docker-buildx-6.x into main

Reviewed-on: #8

.woodpecker/pr-build.yaml

@@ -0,0 +1,26 @@
+# Build validation for pull requests (and pushes to main).
+#
+# Builds the full multi-arch image but does NOT push it anywhere — it only
+# proves the Dockerfile still builds for every supported architecture. This is
+# the gate Renovate automerge waits on: a dependency bump that breaks the build
+# fails this check and will NOT be automerged (and therefore never reaches
+# :stable or the routers).
+#
+# Reports pass/fail status back to Gitea, so it shows up as a required check on
+# the PR.
+
+when:
+  - event: pull_request
+  - event: push
+    branch: main
+
+steps:
+  - name: Build all arches (no push)
+    image: woodpeckerci/plugin-docker-buildx:6.1.0
+    privileged: true
+    settings:
+      repo: mikrotik-tailscale
+      platforms: linux/amd64,linux/arm64,linux/arm/v7
+      dry-run: true
+      build_args:
+        - OCI_VERSION=ci-${CI_COMMIT_SHA}

.woodpecker/release.yaml

@@ -43,7 +43,7 @@ steps:
       - 'printf "PLUGIN_PASSWORD=%s\n" "$(bao kv get -mount secret -field REGISTRY_PASSWORD container-registry)" >> /woodpecker/registry.env'
 
   - name: Build and push multi-arch image
-    image: woodpeckerci/plugin-docker-buildx:5.2.2
+    image: woodpeckerci/plugin-docker-buildx:6.1.0
     privileged: true
     settings:
       registry: gitea.lumpiasty.xyz

docs/DESIGN.md

@@ -28,10 +28,12 @@ Measured flattened rootfs for the arm64 image:
 | arm64  | ~3.5 MB |
 | arm/v7 | ~3.5 MB |
 
-> The extracted rootfs must contain the binary only **once**. If you measure
-> ~7 MB on the device with `du -sx /`, the Dockerfile has reintroduced an
-> overlayfs copy-up — see
-> [Avoiding overlayfs layer duplication](#avoiding-overlayfs-layer-duplication).
+On a deployed RouterOS device the container consumes **~3.7 MiB of flash**
+(measured by `free-hdd-space` delta). Note that `du` *inside* the container
+reports roughly double that (~7 MB) — that is RouterOS block-allocation
+rounding, **not** real usage or duplication; see
+[Avoiding overlayfs layer duplication](#avoiding-overlayfs-layer-duplication)
+for how to measure correctly.
 
 The binary is built with Tailscale's `--extra-small` feature tag set as the
 baseline. Features are opted in explicitly — any new feature Tailscale adds
@@ -73,33 +75,46 @@ the Tailscale binary.
 
 ### Avoiding overlayfs layer duplication
 
-A subtle but important detail: **the final image must not run a `RUN` that
-mutates a directory already populated by an earlier layer**, or the extracted
-on-disk size roughly doubles for that directory's contents.
-
-RouterOS Container uses overlayfs and stores the **extracted** layers on disk.
-Each Dockerfile instruction is its own layer. If `/usr/local/bin/` is created by
-a `COPY` (containing the ~3 MB `tailscale.combined`) and a later `RUN ln -s …`
-adds a symlink *inside that same directory*, overlayfs performs a **copy-up**:
-it copies the entire `/usr/local/bin/` directory — including the 3 MB binary —
-into the new layer's upper dir. RouterOS then extracts both copies to flash, so
-`du -sx /` reports ~7 MB instead of ~3.4 MB for a directory whose only real file
-is 3 MB. (The compressed image hides this — compression dedupes identical blocks
-— which is why it only shows up when you measure the *extracted* rootfs on the
-device.)
+Best practice for the final image: **don't run a `RUN` that mutates a directory
+already populated by an earlier layer.** Each Dockerfile instruction is its own
+layer; if `/usr/local/bin/` is created by a `COPY` (containing the ~3 MB
+`tailscale.combined`) and a later `RUN ln -s …` adds a symlink *inside that same
+directory*, overlayfs performs a **copy-up** of the entire directory — including
+the 3 MB binary — into the new layer. The binary then physically exists in two
+image layers.
 
 The fix: assemble `/usr/local/bin/` completely in the **builder** stage (binary
 + both `argv[0]` symlinks) and bring it into the final image with a **single
 `COPY` layer**, never mutating it afterwards. The Dockerfile does this; don't
-reintroduce a post-`COPY` `RUN` against that path.
-
-To verify the extracted footprint on a deployed router:
+reintroduce a post-`COPY` `RUN` against that path. You can confirm the published
+image carries the binary in exactly one layer:
 
 ```
-/container/shell [find where name=tailscale]
-du -sx /        # expect ~3500 KiB (1 KiB blocks), not ~7000
+docker save <image> -o img.tar && tar xf img.tar -C img/
+# then grep each blob layer for usr/local/bin/tailscale.combined — it must
+# appear in exactly ONE layer.
 ```
 
+Note: this is about keeping the *image* clean. It does **not** change what `du`
+reports on the device — see the measurement note below.
+
+To verify the on-flash footprint on a deployed router, use the **free-space
+delta**, not `du`:
+
+```
+/system/resource/print     # note free-hdd-space before and after adding the container
+```
+
+The container should consume **~3.7 MiB** of flash (e.g. 94.6 → 90.9 MiB free).
+
+Do **not** trust `du` inside the container for this. Busybox `du` reports
+*allocated blocks*, and RouterOS's container store rounds a ~3 MB file up to
+~6 MB of blocks — so `du -sx /` reports ~7 MB even though real flash use is
+~3.7 MB. `ls -la /usr/local/bin` confirms the binary's true content size
+(~3.1 MB) and that it is a single file with two symlinks (no duplication).
+The image itself carries the binary in exactly one layer (verified at the blob
+level); the inflation is purely the filesystem's block accounting.
+
 ## Architecture support
 
 A single Dockerfile builds all three supported RouterOS architectures. The Go
@@ -309,14 +324,35 @@ run **self-hosted** from a Woodpecker cron pipeline (Woodpecker has no native
 Renovate support):
 
 - `renovate.json` — repository rules. All dependencies follow the latest
-  upstream releases (including major versions); each bump arrives as its own PR
-  that the multi-arch build validates before you merge. Base image tags also
-  get their `@sha256` digests refreshed via `pinDigests`. The one special rule:
+  upstream releases; each bump arrives as its own PR. Base image tags also get
+  their `@sha256` digests refreshed via `pinDigests`. Notable rules:
   - `tailscale` only follows **stable** releases — Tailscale uses even minor
     versions for stable (`v1.98.x`) and odd for unstable (`v1.99.x`), so the
     rule filters to even minors.
 - `.woodpecker/renovate.yaml` — the scheduled job that runs `renovate/renovate`
   against this repo.
+- `.woodpecker/pr-build.yaml` — builds all three arches (no push) on every PR
+  and reports status to Gitea. This is the gate for automerge.
+
+### Automerge policy
+
+These updates **automerge** once the PR build passes — they reach `:stable`
+(and the routers) without manual review:
+
+| Update | Automerge? | Why |
+|---|---|---|
+| Tailscale stable (patch **and** minor) | ✅ | the point of the project; the PR build catches breakage |
+| Go / Alpine / busybox **patch** | ✅ | bugfix-only, build-internal |
+| Base-image **digest** refresh (same tag) | ✅ | content refresh, no version change |
+| Go / Alpine / busybox **minor/major** | ❌ manual | larger toolchain/base changes warrant review |
+| Renovate runner, syntax frontend | ❌ manual | tooling — review deliberately |
+
+**Important:** automerge depends on the PR build being a **required status
+check** in Gitea branch protection. The PR build only proves the image *builds*
+for all arches — it does not run the daemon, so a runtime regression in a new
+Tailscale release could still be automerged. That is an accepted trade-off for
+the convenience of unattended Tailscale updates; if a release misbehaves, roll
+back by re-tagging the previous `v…-mt.N` (the immutable tags are kept).
 
 Validate the configs locally:
 

renovate.json

@@ -7,10 +7,12 @@
   ],
   "labels": ["dependencies"],
   "rebaseWhen": "behind-base-branch",
-  "dockerfile": {
-    "pinDigests": true
-  },
   "packageRules": [
+    {
+      "matchManagers": ["dockerfile"],
+      "description": "Keep base-image tags pinned to a digest.",
+      "pinDigests": true
+    },
     {
       "matchDatasources": ["github-releases"],
       "matchPackageNames": ["tailscale/tailscale"],
@@ -18,6 +20,28 @@
       "extractVersion": "^v(?<version>\\d+\\.\\d+\\.\\d+)$",
       "allowedVersions": "/^\\d+\\.\\d*[02468]\\.\\d+$/",
       "ignoreUnstable": true
+    },
+    {
+      "matchDatasources": ["github-releases"],
+      "matchPackageNames": ["tailscale/tailscale"],
+      "description": "Automerge all stable Tailscale releases (patch AND minor) once the PR build passes.",
+      "matchUpdateTypes": ["minor", "patch"],
+      "automerge": true
+    },
+    {
+      "matchManagers": ["dockerfile"],
+      "matchPackageNames": ["golang", "alpine", "busybox"],
+      "description": "Automerge PATCH-only bumps of build components (Go/Alpine/busybox) once the PR build passes; review minor/major manually.",
+      "matchUpdateTypes": ["patch"],
+      "automerge": true
+    },
+    {
+      "matchManagers": ["dockerfile"],
+      "matchUpdateTypes": ["digest", "pinDigest"],
+      "description": "Automerge base-image digest refreshes (same tag, new sha256) once the PR build passes.",
+      "automerge": true
     }
-  ]
+  ],
+  "automergeType": "pr",
+  "platformAutomerge": true
 }