Add cache to container build (#35697)

add mount cache directives to container builds, which speeds up local
builds bypassing node and go package download entirely on second build
and caching go compilation.
drop job level split on regular/rootless, which allows to reuse the
previously made stage for rootless, skipping duplicate builds in CI.

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

Dockerfile

@@ -1,8 +1,8 @@
+# syntax=docker/dockerfile:1
 # Build stage
 FROM docker.io/library/golang:1.25-alpine3.22 AS build-env
 
-ARG GOPROXY
-ENV GOPROXY=${GOPROXY:-direct}
+ARG GOPROXY=direct
 
 ARG GITEA_VERSION
 ARG TAGS="sqlite sqlite_unlock_notify"
@@ -14,22 +14,24 @@ RUN apk --no-cache add \
     build-base \
     git \
     nodejs \
-    npm \
-    && npm install -g pnpm@10 \
-    && rm -rf /var/cache/apk/*
+    pnpm
 
-# Setup repo
-COPY . ${GOPATH}/src/code.gitea.io/gitea
 WORKDIR ${GOPATH}/src/code.gitea.io/gitea
+# Use COPY but not "mount" because some directories like "node_modules" contain platform-depended contents and these directories need to be ignored.
+# ".git" directory will be mounted later separately for getting version data.
+# TODO: in the future, maybe we can pre-build the frontend assets on one platform and share them for different platforms, the benefit is that it won't be affected by webpack plugin compatibility problems, then the working directory can be fully mounted and the COPY is not needed.
+COPY --exclude=.git/ . .
 
-# Checkout version if set
-RUN if [ -n "${GITEA_VERSION}" ]; then git checkout "${GITEA_VERSION}"; fi \
- && make clean-all build
+# Build gitea, .git mount is required for version data
+RUN --mount=type=cache,target=/go/pkg/mod \
+    --mount=type=cache,target="/root/.cache/go-build" \
+    --mount=type=cache,target=/root/.local/share/pnpm/store \
+    --mount=type=bind,source=".git/",target=".git/" \
+    make
 
-# Copy local files
 COPY docker/root /tmp/local
 
-# Set permissions
+# Set permissions for builds that made under windows which strips the executable bit from file
 RUN chmod 755 /tmp/local/usr/bin/entrypoint \
               /tmp/local/usr/local/bin/* \
               /tmp/local/etc/s6/gitea/* \
@@ -37,8 +39,7 @@ RUN chmod 755 /tmp/local/usr/bin/entrypoint \
               /tmp/local/etc/s6/.s6-svscan/* \
               /go/src/code.gitea.io/gitea/gitea
 
-FROM docker.io/library/alpine:3.22
-LABEL maintainer="maintainers@gitea.io"
+FROM docker.io/library/alpine:3.22 AS gitea
 
 EXPOSE 22 3000
 
@@ -53,8 +54,7 @@ RUN apk --no-cache add \
     s6 \
     sqlite \
     su-exec \
-    gnupg \
-    && rm -rf /var/cache/apk/*
+    gnupg
 
 RUN addgroup \
     -S -g 1000 \
@@ -68,6 +68,9 @@ RUN addgroup \
     git && \
   echo "git:*" | chpasswd -e
 
+COPY --from=build-env /tmp/local /
+COPY --from=build-env /go/src/code.gitea.io/gitea/gitea /app/gitea/gitea
+
 ENV USER=git
 ENV GITEA_CUSTOM=/data/gitea
 
@@ -75,6 +78,3 @@ VOLUME ["/data"]
 
 ENTRYPOINT ["/usr/bin/entrypoint"]
 CMD ["/usr/bin/s6-svscan", "/etc/s6"]
-
-COPY --from=build-env /tmp/local /
-COPY --from=build-env /go/src/code.gitea.io/gitea/gitea /app/gitea/gitea