fix: avoid dependency rebuild on version-only bumps in Docker

Add a prep stage that normalizes the root package version to 0.0.0 so
BuildKit's content-based caching keeps the dependency layer cached when
only the version in Cargo.toml/Cargo.lock changes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mikkeldamsgaard

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- Docker dependency cache now survives version-only bumps by normalizing the root package version in a preparatory build stage.
+
 ## [1.3.0] - 2026-03-12
 
 ### Added

Dockerfile

@@ -1,8 +1,17 @@
+# Normalize root package version so the dependency cache survives version-only bumps.
+# BuildKit uses content-based caching for COPY --from; the sed output is identical
+# when only the version changed, so the expensive cargo build layer stays cached.
+FROM rust:1.88-alpine AS deps
+WORKDIR /src
+COPY Cargo.toml Cargo.lock ./
+RUN sed -i '/^name = "initium"/{n;s/^version = ".*"/version = "0.0.0"/;}' Cargo.toml && \
+    sed -i '/^name = "initium"/{n;s/^version = ".*"/version = "0.0.0"/;}' Cargo.lock
+
 FROM rust:1.88-alpine AS builder
 ARG VERSION=dev
 RUN apk add --no-cache musl-dev openssl-dev openssl-libs-static perl
 WORKDIR /src
-COPY Cargo.toml Cargo.lock ./
+COPY --from=deps /src/Cargo.toml /src/Cargo.lock ./
 RUN mkdir src && echo 'fn main() {}' > src/main.rs && \
     cargo build --release && \
     rm -rf src target/release/deps/initium* target/release/initium*

jyq.Dockerfile

@@ -1,8 +1,17 @@
+# Normalize root package version so the dependency cache survives version-only bumps.
+# BuildKit uses content-based caching for COPY --from; the sed output is identical
+# when only the version changed, so the expensive cargo build layer stays cached.
+FROM rust:1.88-alpine AS deps
+WORKDIR /src
+COPY Cargo.toml Cargo.lock ./
+RUN sed -i '/^name = "initium"/{n;s/^version = ".*"/version = "0.0.0"/;}' Cargo.toml && \
+    sed -i '/^name = "initium"/{n;s/^version = ".*"/version = "0.0.0"/;}' Cargo.lock
+
 FROM rust:1.88-alpine AS builder
 ARG VERSION=dev
 RUN apk add --no-cache musl-dev openssl-dev openssl-libs-static perl
 WORKDIR /src
-COPY Cargo.toml Cargo.lock ./
+COPY --from=deps /src/Cargo.toml /src/Cargo.lock ./
 RUN mkdir src && echo 'fn main() {}' > src/main.rs && \
     cargo build --release && \
     rm -rf src target/release/deps/initium* target/release/initium*