Port bashbrew to use Go modules instead of GB

Something in here also fixes the "missing build output on error" bug we've been seeing on Jenkins (see https://doi-janky.infosiftr.net/job/multiarch/job/arm32v7/job/rabbitmq/184/console for example).

.travis.yml

@@ -1,15 +1,9 @@
 language: go
-go: 1.7.x
-
-# allow for use of Docker-based workers
-sudo: false
-
-install:
-    - go get -v -u github.com/constabulary/gb/...
+go: 1.12.x
 
 before_script:
     - env | sort
-    - ( cd bashbrew/go && gb build )
+    - ./bashbrew/bashbrew.sh --help > /dev/null
     - export PATH="$PWD/bashbrew/go/bin:$PATH"
 
 script:

Dockerfile

@@ -35,11 +35,9 @@ RUN mkdir -p "$BASHBREW_CACHE" \
 WORKDIR $DIR
 COPY . $DIR
 
-RUN set -ex; \
-	cd bashbrew/go; \
-	export GOPATH="$PWD:$PWD/vendor"; \
-	cd src; \
-	CGO_ENABLED=0 go install -v ./...
+RUN set -eux; \
+	CGO_ENABLED=0 ./bashbrew/bashbrew.sh --help > /dev/null; \
+	cp -vL bashbrew/go/bin/bashbrew /usr/local/bin/
 
 VOLUME $BASHBREW_CACHE
 

bashbrew/.dockerignore

@@ -3,7 +3,4 @@
 .dockerignore
 Dockerfile*
 go/bin
-go/pkg
-go/vendor/bin
-go/vendor/pkg
 !.bashbrew-arch-to-goenv.sh

bashbrew/Dockerfile.release

@@ -5,7 +5,6 @@ RUN apk add --no-cache \
 		gnupg
 
 WORKDIR /usr/src/bashbrew
-ENV GOPATH /usr/src/bashbrew:/usr/src/bashbrew/vendor
 ENV CGO_ENABLED 0
 
 ENV BASHBREW_ARCHES \
@@ -73,7 +72,8 @@ RUN set -euxo pipefail; \
 				-ldflags '-s -w' \
 				-tags netgo -installsuffix netgo \
 				-o "$targetBin" \
-				./src/bashbrew \
+				-mod vendor \
+				bashbrew/src/bashbrew \
 			; \
 			ls -lAFh "$targetBin"; \
 			file "$targetBin"; \

bashbrew/bashbrew.sh

@@ -3,10 +3,6 @@ set -e
 
 dir="$(dirname "$(readlink -f "$BASH_SOURCE")")"
 
-if ! command -v gb &> /dev/null; then
-	( set -x && go get github.com/constabulary/gb/... )
-fi
-
-( cd "$dir/go" && gb build > /dev/null )
+( cd "$dir/go" && go build -o bin/bashbrew -mod vendor bashbrew/src/bashbrew > /dev/null )
 
 exec "$dir/go/bin/bashbrew" "$@"

bashbrew/go/go.mod

@@ -0,0 +1,10 @@
+module bashbrew
+
+require (
+	github.com/codegangsta/cli v1.20.0
+	github.com/docker-library/go-dockerlibrary v0.0.0-20190129000321-7e50189a05d4
+	golang.org/x/crypto v0.0.0-20190325154230-a5d413f7728c // indirect
+	golang.org/x/sys v0.0.0-20190322080309-f49334f85ddc // indirect
+	pault.ag/go/debian v0.0.0-20190109175134-a131cb0ae041
+	pault.ag/go/topsort v0.0.0-20160530003732-f98d2ad46e1a
+)

bashbrew/go/go.sum

@@ -0,0 +1,15 @@
+github.com/codegangsta/cli v1.20.0 h1:iX1FXEgwzd5+XN6wk5cVHOGQj6Q3Dcp20lUeS4lHNTw=
+github.com/codegangsta/cli v1.20.0/go.mod h1:/qJNoX69yVSKu5o4jLyXAENLRyk1uhi7zkbQ3slBdOA=
+github.com/docker-library/go-dockerlibrary v0.0.0-20190129000321-7e50189a05d4 h1:Jl830zF5XyeMipP9Ag2J64TAeheWDvOsqLuaDHn4pb8=
+github.com/docker-library/go-dockerlibrary v0.0.0-20190129000321-7e50189a05d4/go.mod h1:ijRhN3WM71dD8TfohKoUdX46BT2uz/Ek5O+5PINI880=
+github.com/kjk/lzma v0.0.0-20161016003348-3fd93898850d/go.mod h1:phT/jsRPBAEqjAibu1BurrabCBNTYiVI+zbmyCZJY6Q=
+github.com/xi2/xz v0.0.0-20171230120015-48954b6210f8/go.mod h1:HUYIGzjTL3rfEspMxjDjgmT5uz5wzYJKVo23qUhYTos=
+golang.org/x/crypto v0.0.0-20190103213133-ff983b9c42bc/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
+golang.org/x/crypto v0.0.0-20190325154230-a5d413f7728c h1:Vj5n4GlwjmQteupaxJ9+0FNOmBrHfq7vN4btdGoDZgI=
+golang.org/x/crypto v0.0.0-20190325154230-a5d413f7728c/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190322080309-f49334f85ddc/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+pault.ag/go/debian v0.0.0-20190109175134-a131cb0ae041 h1:LmTwXQVDWXMigTB88hFtd6mc3l5eLAlgdtfPI0F69bQ=
+pault.ag/go/debian v0.0.0-20190109175134-a131cb0ae041/go.mod h1:e7Gva9AMoKtUKYJ1G9kIesbh+4VS2JnAOS8VWafyTCk=
+pault.ag/go/topsort v0.0.0-20160530003732-f98d2ad46e1a h1:WwS7vlB5H2AtwKj1jsGwp2ZLud1x6WXRXh2fXsRqrcA=
+pault.ag/go/topsort v0.0.0-20160530003732-f98d2ad46e1a/go.mod h1:INqx0ClF7kmPAMk2zVTX8DRnhZ/yaA/Mg52g8KFKE7k=

bashbrew/go/src/bashbrew/main.go

@@ -70,8 +70,12 @@ func main() {
 
 	// TODO add "Description" to app and commands (for longer-form description of their functionality)
 
-	cli.VersionFlag.Name = "version" // remove "-v" from VersionFlag
-	cli.HelpFlag.Name = "help, h, ?" // add "-?" to HelpFlag
+	// add "-?" to HelpFlag
+	cli.HelpFlag = cli.BoolFlag{
+		Name:  "help, h, ?",
+		Usage: "show help",
+	}
+
 	app.Flags = []cli.Flag{
 		cli.BoolFlag{
 			Name:   "debug",