feat: read built timestamp from git

Author: sschnabe

Dockerfile

@@ -6,6 +6,10 @@
 FROM docker.io/library/bash:5.2.37@sha256:01a15c6f48f6a3c08431cd77e11567823530b18159889dca3b7309b707beef91
 SHELL ["/usr/local/bin/bash", "-u", "-e", "-o", "pipefail", "-c"]
 
+# workaround until we have a env `CI_COMMIT_TIMESTAMP`
+# see https://github.com/woodpecker-ci/woodpecker/issues/5245
+RUN apk add git~=2 --no-cache
+
 RUN ARCH=$(uname -m) && \
 	[[ $ARCH == x86_64 ]] && export SUFFIX=amd64; \
 	[[ $ARCH == aarch64 ]] && export SUFFIX=arm64; \

README.md

@@ -72,21 +72,21 @@ docker run --rm --user=$(id -u) --volume=$HOME:$HOME:ro --workdir=$PWD --env=PLU
 
 ## Settings
 
-| Settings Name       | Environment              | Default          | Description                                                                                     |
-| ------------------- | ------------------------ | ---------------- | ----------------------------------------------------------------------------------------------- |
-| `addr`              | PLUGIN_ADDR              | `$BUILDKIT_HOST` | Buildkit host to use.                                                                           |
-| `frontend`          | PLUGIN_FRONTEND          | `dockerfile.v0`  | Only dockerfile frontend supported right now                                                    |
-| `context`           | PLUGIN_CONTEXT           | `$PWD`           | Context directory to use for build                                                              |
-| `dockerfile`        | PLUGIN_DOCKERFILE        | `Dockerfile`     | Dockerfile to use.                                                                              |
-| `target`            | PLUGIN_TARGET            | `none`           | Dockerfile target                                                                               |
-| `build-args`        | PLUGIN_BUILD_ARGS        | `none`           | Build args to pass to build                                                                     |
-| `platform`          | PLUGIN_PLATFORM          | `none`           | Target platform for container image.                                                            |
-| `source-epoch-date` | PLUGIN_SOURCE_DATE_EPOCH | `0`              | Timestamp to use for reproduceable builds.                                                      |
-| `name`              | PLUGIN_NAME              | `none`           | Images names where to push the image.                                                           |
-| `annotation`        | PLUGIN_ANNOTATION        | `none`           | Annotations (also known as labels) to add to image                                              |
-| `push`              | PLUGIN_PUSH              | `true`           | Push images if output names are set.                                                            |
-| `auth`              | PLUGIN_AUTH              | `none`           | Auth for private registries                                                                     |
-| `env-file`          | PLUGIN_ENV_FILE          | `none`           | Source environment values from given file                                                       |
+| Settings Name       | Environment              | Default                     | Description                                        |
+| ------------------- | ------------------------ | --------------------------- | -------------------------------------------------- |
+| `addr`              | PLUGIN_ADDR              | `$BUILDKIT_HOST`            | Buildkit host to use.                              |
+| `frontend`          | PLUGIN_FRONTEND          | `dockerfile.v0`             | Only dockerfile frontend supported right now       |
+| `context`           | PLUGIN_CONTEXT           | `$PWD`                      | Context directory to use for build                 |
+| `dockerfile`        | PLUGIN_DOCKERFILE        | `Dockerfile`                | Dockerfile to use.                                 |
+| `target`            | PLUGIN_TARGET            | `none`                      | Dockerfile target                                  |
+| `build-args`        | PLUGIN_BUILD_ARGS        | `none`                      | Build args to pass to build                        |
+| `platform`          | PLUGIN_PLATFORM          | `none`                      | Target platform for container image.               |
+| `source-epoch-date` | PLUGIN_SOURCE_DATE_EPOCH | `git log -1 --format="%at"` | Timestamp to use for reproduceable builds.         |
+| `name`              | PLUGIN_NAME              | `none`                      | Images names where to push the image.              |
+| `annotation`        | PLUGIN_ANNOTATION        | `none`                      | Annotations (also known as labels) to add to image |
+| `push`              | PLUGIN_PUSH              | `true`                      | Push images if output names are set.               |
+| `auth`              | PLUGIN_AUTH              | `none`                      | Auth for private registries                        |
+| `env-file`          | PLUGIN_ENV_FILE          | `none`                      | Source environment values from given file          |
 
 ## Alternatives
 

entrypoint.sh

@@ -1,6 +1,15 @@
 #!/usr/bin/env bash
 set -eu;
 
+##
+## workaround until we have a env `CI_COMMIT_TIMESTAMP`
+## see https://github.com/woodpecker-ci/woodpecker/issues/5245
+##
+
+if [[ -z "${CI_COMMIT_TIMESTAMP:-}" ]]; then
+	CI_COMMIT_TIMESTAMP=$(git log -1 --format="%at")
+fi
+
 ##
 ## check input
 ##
@@ -27,7 +36,7 @@ if [[ "$BUILDCTL_FRONTEND" != "dockerfile.v0" ]]; then
 	exit 1
 fi
 
-SOURCE_DATE_EPOCH=${PLUGIN_SOURCE_DATE_EPOCH:-0}
+SOURCE_DATE_EPOCH=${PLUGIN_SOURCE_DATE_EPOCH:-${CI_COMMIT_TIMESTAMP:-0}}
 
 if [[ -n "${PLUGIN_AUTH:-}" ]]; then
 	echo "$PLUGIN_AUTH" | jq -r 'to_entries|map({(.key):{"auth":(.value.username+":"+.value.password)|@base64}})|add|{"auths":.}' > "$HOME/.docker/config.json"