user: move userns package to separate module, and retract v0.2.0

commit 86870e7 integrated the userns package
into the github.com/moby/sys/user module, which was included in the v0.2.0
version of the module.

Upon further discussion with maintainers, this may not have been a good
choice; the userns package is related to user-namespaces (uid/gid-mapping),
and while there are some tangential relations with "user", we shouldn't
conflate these concepts by putting both into the same module.

Some downstream projects (containerd, moby, containerd/cgroups) already
accepted patches to switch to the package that's part of the moby/sys/user
module, but none of those patches made it into a release.

This patch:

- moves the userns package to a separate module
- retracts the moby/sys/user v0.2.0 release
- downgrades the minimum go version update for the moby/sys/user module
  to go1.17. Note that CI is no longer testing go1.17, but go1.18 as minimum.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

.github/workflows/test.yml

@@ -14,6 +14,9 @@ jobs:
         go-version: ${{ matrix.go-version }}
     - name: Checkout code
       uses: actions/checkout@v4
+    - if: ${{ matrix.go-version == '1.18.x' }}
+      run: |
+        echo 'PACKAGES="mountinfo mount sequential signal symlink user"' >> $GITHUB_ENV
     - name: go mod tidy
       run: |
         make tidy

Makefile

@@ -1,4 +1,4 @@
-PACKAGES ?= mountinfo mount sequential signal symlink user
+PACKAGES ?= mountinfo mount sequential signal symlink user userns # IMPORTANT: when updating this list, also update the conditional one in .github/workflows/test.yml
 BINDIR ?= _build/bin
 CROSS ?= linux/arm linux/arm64 linux/ppc64le linux/s390x \
 	freebsd/amd64 openbsd/amd64 darwin/amd64 darwin/arm64 windows/amd64
@@ -16,18 +16,14 @@ clean:
 test: test-local
 	set -eu; \
 	for p in $(PACKAGES); do \
-		if $p = user && go version | grep -qv go1.18; then \
-			(cd $$p; go test $(RUN_VIA_SUDO) -v .); \
-		fi \
+		(cd $$p; go test $(RUN_VIA_SUDO) -v .); \
 	done
 
 .PHONY: tidy
 tidy:
 	set -eu; \
 	for p in $(PACKAGES); do \
-		if $p = user && go version | grep -qv go1.18; then \
-			(cd $$p; go mod tidy); \
-		fi \
+		(cd $$p; go mod tidy); \
 	done
 
 # Test the mount module against the local mountinfo source code instead of the
@@ -46,11 +42,9 @@ lint: $(BINDIR)/golangci-lint
 	$(BINDIR)/golangci-lint version
 	set -eu; \
 	for p in $(PACKAGES); do \
-		if $p = user && go version | grep -qv go1.18; then \
-			(cd $$p; \
-			go mod download; \
-			../$(BINDIR)/golangci-lint run); \
-		fi \
+		(cd $$p; \
+		go mod download; \
+		../$(BINDIR)/golangci-lint run); \
 	done
 
 $(BINDIR)/golangci-lint: $(BINDIR)

user/go.mod

@@ -1,5 +1,7 @@
 module github.com/moby/sys/user
 
-go 1.21
+go 1.17
 
 require golang.org/x/sys v0.1.0
+
+retract v0.2.0 // Package github.com/moby/sys/user/userns was included in this module, but should've been a separate module; see https://github.com/moby/sys/pull/140#issuecomment-2250644304.

userns/go.mod

@@ -0,0 +1,3 @@
+module github.com/moby/sys/userns
+
+go 1.21