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.rootless

@@ -1,40 +1,39 @@
+# 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"
 ENV TAGS="bindata timetzdata $TAGS"
 ARG CGO_EXTRA_CFLAGS
 
-#Build deps
+# Build deps
 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
+# See the comments in Dockerfile
+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/rootless /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/local/bin/* \
               /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-rootless
 
 EXPOSE 2222 3000
 
@@ -46,8 +45,7 @@ RUN apk --no-cache add \
     git \
     curl \
     gnupg \
-    openssh-keygen \
-    && rm -rf /var/cache/apk/*
+    openssh-keygen
 
 RUN addgroup \
     -S -g 1000 \