[release] fix nullglob issue

- add communication section
- remove systemd-nspawn section

.build.yml

@@ -14,7 +14,7 @@ tasks:
   - lint: |
       make -C undocker -O -j$(nproc) lint
   - binaries: |
-      make -C undocker -O -j$(nproc) sha256sum.txt
-      cat undocker/sha256sum.txt
+      make -C undocker -O -j$(nproc) all
+      cat undocker/sha256sum-*.txt
 artifacts:
   - undocker/coverage.html

.gitignore

@@ -1,3 +1,4 @@
+/undocker
 /undocker-*
 coverage.html
 sha256sum.txt*

Makefile

@@ -1,6 +1,5 @@
 SCRIPTS = $(shell awk '/#!\/bin\/(ba)?sh/&&FNR==1{print FILENAME}' $(shell git ls-files))
 GODEPS = $(shell git ls-files '*.go' go.mod go.sum)
-GOBIN = $(shell go env GOPATH)/bin/
 GOOSARCHS = $(sort darwin/amd64 linux/amd64)
 
 VSN ?= $(shell git describe --dirty)
@@ -24,12 +23,15 @@ $(foreach goosarch,$(GOOSARCHS),\
 	$(eval $(call undockertarget,$(word 1,$(subst /, ,$(goosarch))),$(word 2,$(subst /, ,$(goosarch))))))
 
 .PHONY: all
-all: $(UNDOCKERS)
+all: $(UNDOCKERS) sha256sum-$(VSN).txt
+
+.PHONY: sha256sum-asc
+sha256sum-asc: sha256sum-$(VSN).txt.asc
 
 .PHONY: lint
 lint:
 	go vet ./...
-	$(GOBIN)staticcheck -f stylish ./...
+	$(shell go env GOPATH)/bin/staticcheck -f stylish ./...
 	shellcheck $(SCRIPTS)
 
 .INTERMEDIATE: coverage.out
@@ -39,12 +41,12 @@ coverage.out: $(GODEPS)
 coverage.html: coverage.out
 	go tool cover -html=$< -o $@
 
-sha256sum.txt: $(UNDOCKERS)
+sha256sum-$(VSN).txt: $(UNDOCKERS)
 	sha256sum $(UNDOCKERS) > $@
 
-sha256sum.txt.asc: sha256sum.txt
+sha256sum-$(VSN).txt.asc: sha256sum-$(VSN).txt
 	gpg --clearsign $<
 
 .PHONY: clean
 clean:
-	rm -f undocker-*-v* coverage.html sha256sum.txt sha256sum.txt.asc
+	rm -f undocker-*-v* coverage.html sha256sum*.txt sha256sum*.txt.asc

README.md

@@ -23,16 +23,12 @@ Undocker has no dependencies outside Golang stdlib.
 Installation
 ------------
 
-We recommend using [officially released binaries][3]. To build the project
-instead, run:
+You may use [officially released binaries][3], or build it:
 
 ```
 $ make undocker
 ```
 
-The number of officially released binaries is quite limited. If you'd like me
-to expand a list, please contribute a patch to the Makefile.
-
 Usage: convert docker image to rootfs
 -------------------------------------
 
@@ -40,50 +36,41 @@ Download `busybox` docker image from docker hub and convert it to a rootfs:
 
 ```
 $ skopeo copy docker://docker.io/busybox:latest docker-archive:busybox.tar
-$ undocker busybox.tar - | tar -tv | head -10
-drwxr-xr-x 0/0               0 2021-05-17 22:07 bin/
--rwxr-xr-x 0/0         1149184 2021-05-17 22:07 bin/[
-hrwxr-xr-x 0/0               0 2021-05-17 22:07 bin/[[ link to bin/[
-hrwxr-xr-x 0/0               0 2021-05-17 22:07 bin/acpid link to bin/[
-hrwxr-xr-x 0/0               0 2021-05-17 22:07 bin/add-shell link to bin/[
-hrwxr-xr-x 0/0               0 2021-05-17 22:07 bin/addgroup link to bin/[
-hrwxr-xr-x 0/0               0 2021-05-17 22:07 bin/adduser link to bin/[
-hrwxr-xr-x 0/0               0 2021-05-17 22:07 bin/adjtimex link to bin/[
-hrwxr-xr-x 0/0               0 2021-05-17 22:07 bin/ar link to bin/[
-hrwxr-xr-x 0/0               0 2021-05-17 22:07 bin/arch link to bin/[
+$ undocker busybox.tar - | tar -xv | sponge | head -10; echo '<...>'
+bin/
+bin/[
+bin/[[
+bin/acpid
+bin/add-shell
+bin/addgroup
+bin/adduser
+bin/adjtimex
+bin/ar
+bin/arch
+<...>
 ```
 
-You can also refer [here][2] for other ways to download Docker images. There
-are many.
+Refer [here][2] for other ways to download Docker images. There are many.
 
-Converting a [1.1GB Docker image with 77
-layers](https://hub.docker.com/r/homeassistant/home-assistant) takes around 4
-seconds and on a reasonably powerful Intel laptop.
+On author's laptop converting a [1.1GB Docker image with 77
+layers](https://hub.docker.com/r/homeassistant/home-assistant) takes around 3
+seconds and uses ~65MB of residential memory.
 
-Usage example: systemd-nspawn
------------------------------
-
-Start with systemd-nspawn:
-
-```
-systemd-nspawn -D $PWD busybox httpd -vfp 8080
-```
-
-Usage example: plain old systemd
---------------------------------
+Usage example: systemd
+----------------------
 
 ```
 systemd-run \
   --wait --pty --collect --service-type=exec \
+  -p RootDirectory=$PWD \
+  -p ProtectProc=invisible \
   -p PrivateUsers=true \
   -p DynamicUser=yes \
-  -p ProtectProc=invisible \
-  -p RootDirectory=$PWD \
   -- busybox httpd -vfp 8080
 ```
 
-Good things like `PrivateUsers`, `DynamicUser`, `ProtectProc` and other
-[systemd protections][1] are available, just like to any systemd unit.
+[Systemd protections][1] like `PrivateUsers`, `DynamicUser`, `ProtectProc` and
+others are available, just like to any systemd unit.
 
 Similar Projects
 ----------------
@@ -102,7 +89,7 @@ Contributions
 
 The following contributions may be accepted:
 
-- Pull requests (patchsets) with accompanying tests.
+- Patchsets, with accompanying tests.
 - Regression reports.
 
 If you found a container that undocker cannot extract, or extracts incorrectly
@@ -113,6 +100,12 @@ Reports of regression reports must provide examples of "works before" and "does
 not work after". Issues without an accompanying patch will most likely be
 rejected.
 
+Communication
+-------------
+
+Use [~motiejus/undocker@lists.sr.ht](mailto:~motiejus/undocker@lists.sr.ht) for
+questions or patches. Subscribe [here][4].
+
 LICENSE
 -------
 
@@ -121,3 +114,4 @@ MIT
 [1]: https://www.freedesktop.org/software/systemd/man/systemd.exec.html
 [2]: https://fly.io/blog/docker-without-docker/
 [3]: http://git.sr.ht/~motiejus/undocker
+[4]: https://lists.sr.ht/~motiejus/undocker

release

@@ -9,7 +9,14 @@ err() {
 git status --porcelain | grep -q "" &&
     err "working tree is dirty, commit your changes first."
 
-[[ ! "$1" =~ ^v([0-9]+)\.([0-9]+)(\.([0-9]+))?$ ]] && \
+# https://raimue.blog/2010/09/09/bash-for-loop-with-glob-patterns/
+shopt -s nullglob
+for file in sha256sum-*; do
+    err "found $file from previous release, delete it first"
+done
+shopt -u nullglob
+
+[[ "$1" =~ ^v([0-9]+)\.([0-9]+)(\.([0-9]+))?$ ]] || \
     err "arg1 accepts the following formats: v1.0 v1.0.0"
 
 git tag | grep -q "^$1$" &&
@@ -17,7 +24,7 @@ git tag | grep -q "^$1$" &&
 
 last_tag=$(git tag | tail -1)
 
-make -B -j"$(nproc)" VSN="$1" sha256sum.txt.asc
+make -B -j"$(nproc)" VSN="$1" sha256sum-asc
 
 {
     echo undocker "$1"
@@ -27,6 +34,6 @@ make -B -j"$(nproc)" VSN="$1" sha256sum.txt.asc
     echo
     echo
     echo sha256sums of released binaries:
-    cat sha256sum.txt
+    cat sha256sum-*.txt
     echo
 } | git tag -u motiejus@jakstys.lt -F - "$1"

rootfs/rootfs.go

@@ -146,9 +146,8 @@ func Flatten(rd io.ReadSeeker, w io.Writer) (_err error) {
 	defer func() {
 		// Avoiding use of multierr: if error is present, return
 		// that. Otherwise return whatever `Close` returns.
-		err1 := tw.Close()
-		if _err == nil {
-			_err = err1
+		if err := tw.Close(); err != nil && _err == nil {
+			_err = err
 		}
 	}()
 	// iterate through all layers, all files, and write files.