feat: install most dependencies in cacheable layer, before adding main

Instead of requiring the whole stack to be reinstalled whenever a specific version (e.g. main) causes a cache fail, this aims to have stable default version with a second-stage installation of the potentially-modified versions of eicrecon and juggler. This should allow all builds to cache the first installation in virtually all cases, leading to faster builds.

containers/jug/dev.Dockerfile

@@ -117,14 +117,29 @@ RUN git clone --filter=tree:0 https://github.com/${KEY4HEPSPACK_ORGREPO}.git ${K
 ## ========================================================================================
 FROM spack as builder
 
-## Setup our custom environment (secret mount for write-enabled mirror)
+## 1. Setup our default environment (secret mount for write-enabled mirror)
 COPY --from=spack-environment . /opt/spack-environment/
 ARG ENV=dev
-ARG JUGGLER_VERSION="main"
+ENV SPACK_ENV=/opt/spack-environment/${ENV}
+RUN --mount=type=cache,target=/ccache,id=${TARGETPLATFORM}              \
+    --mount=type=cache,target=/var/cache/spack                          \
+    --mount=type=secret,id=mirrors,target=/opt/spack/etc/spack/mirrors.yaml \
+    source $SPACK_ROOT/share/spack/setup-env.sh                         \
+ && export CCACHE_DIR=/ccache                                           \
+ && spack buildcache update-index local                                 \
+ && spack buildcache update-index eics3rw                               \
+ && spack env activate --dir ${SPACK_ENV}                               \
+ && make --jobs ${jobs} --keep-going --directory /opt/spack-environment \
+    SPACK_ENV=${SPACK_ENV}                                              \
+    BUILDCACHE_MIRROR="local eics3rw"                                   \
+ && ccache --show-stats                                                 \
+ && ccache --zero-stats
+
+## 2. Setup our environment with custom versions (on top of cached layer)
+ARG JUGGLER_VERSION=""
+ARG EICRECON_VERSION=""
 ADD https://eicweb.phy.anl.gov/api/v4/projects/EIC%2Fjuggler/repository/tree?ref=${JUGGLER_VERSION} /tmp/juggler.json
-ARG EICRECON_VERSION="main"
 ADD https://api.github.com/repos/eic/eicrecon/commits/${EICRECON_VERSION} /tmp/eicrecon.json
-ENV SPACK_ENV=/opt/spack-environment/${ENV}
 RUN --mount=type=cache,target=/ccache,id=${TARGETPLATFORM}              \
     --mount=type=cache,target=/var/cache/spack                          \
     --mount=type=secret,id=mirrors,target=/opt/spack/etc/spack/mirrors.yaml \
@@ -133,8 +148,13 @@ RUN --mount=type=cache,target=/ccache,id=${TARGETPLATFORM}              \
  && spack buildcache update-index local                                 \
  && spack buildcache update-index eics3rw                               \
  && spack env activate --dir ${SPACK_ENV}                               \
- && spack add juggler@git.${JUGGLER_VERSION}                            \
- && spack add eicrecon@git.${EICRECON_VERSION}                          \
+ && if [ -n ${JUGGLER_VERSION} ] ; then                                 \
+      spack config add "packages:juggler::require:['@git.${JUGGLER_VERSION}']" ; \
+    fi                                                                  \
+ && if [ -n ${EICRECON_VERSION} ] ; then                                \
+      spack config add "packages:eicrecon::require:['@git.${EICRECON_VERSION}']" ; \
+    fi                                                                  \
+ && spack concretize --force --fresh                                    \
  && make --jobs ${jobs} --keep-going --directory /opt/spack-environment \
     SPACK_ENV=${SPACK_ENV}                                              \
     BUILDCACHE_MIRROR="local eics3rw"                                   \