feat: read built timestamp from git

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

@@ -73,7 +73,7 @@ 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                 |
@@ -81,7 +81,7 @@ docker run --rm --user=$(id -u) --volume=$HOME:$HOME:ro --workdir=$PWD --env=PLU
 | `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.                                                      |
+| `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.               |

entrypoint.sh

@@ -1,6 +1,16 @@
 #!/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 "${CI_COMMIT_TIMESTAMP:-}" ]]; then
+	git config --global --add safe.directory "$PWD"
+	CI_COMMIT_TIMESTAMP=$(git log -1 --format="%at")
+fi
+
 ##
 ## check input
 ##
@@ -27,7 +37,7 @@ if [[ "$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"