Move docker dep commands to earlier in the build

This will let Docker cache the results of the vendor dependencies.
Making re-builds during testing faster.

Also clean-up spurious test & rm in ./configure

CHANGELOG.md

@@ -31,6 +31,7 @@
 
 ## Changes since v3.2.0
 
+- [#209](https://github.com/pusher/outh2_proxy/pull/209) Improve docker build caching of layers (@dekimsey)
 - [#186](https://github.com/pusher/oauth2_proxy/pull/186) Make config consistent (@JoelSpeed)
 - [#187](https://github.com/pusher/oauth2_proxy/pull/187) Move root packages to pkg folder (@JoelSpeed)
 - [#65](https://github.com/pusher/oauth2_proxy/pull/65) Improvements to authenticate requests with a JWT bearer token in the `Authorization` header via

Dockerfile

@@ -7,11 +7,14 @@ RUN curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.s
 
 # Copy sources
 WORKDIR $GOPATH/src/github.com/pusher/oauth2_proxy
-COPY . .
 
 # Fetch dependencies
+COPY Gopkg.toml Gopkg.lock ./
 RUN dep ensure --vendor-only
 
+# Now pull in our code
+COPY . .
+
 # Build binary and make sure there is at least an empty key file.
 #  This is useful for GCP App Engine custom runtime builds, because
 #  you cannot use multiline variables in their app.yaml, so you have to

Dockerfile.arm64

@@ -7,11 +7,14 @@ RUN curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.s
 
 # Copy sources
 WORKDIR $GOPATH/src/github.com/pusher/oauth2_proxy
-COPY . .
 
 # Fetch dependencies
+COPY Gopkg.toml Gopkg.lock ./
 RUN dep ensure --vendor-only
 
+# Now pull in our code
+COPY . .
+
 # Build binary and make sure there is at least an empty key file.
 #  This is useful for GCP App Engine custom runtime builds, because
 #  you cannot use multiline variables in their app.yaml, so you have to

Dockerfile.armv6

@@ -7,11 +7,14 @@ RUN curl -sfL https://install.goreleaser.com/github.com/golangci/golangci-lint.s
 
 # Copy sources
 WORKDIR $GOPATH/src/github.com/pusher/oauth2_proxy
-COPY . .
 
 # Fetch dependencies
+COPY Gopkg.toml Gopkg.lock ./
 RUN dep ensure --vendor-only
 
+# Now pull in our code
+COPY . .
+
 # Build binary and make sure there is at least an empty key file.
 #  This is useful for GCP App Engine custom runtime builds, because
 #  you cannot use multiline variables in their app.yaml, so you have to

configure

@@ -116,9 +116,7 @@ check_go_env() {
 
 cd ${0%/*}
 
-if [ ! -f .env ]; then
-  rm .env
-fi
+rm -fv .env
 
 check_for make
 check_for awk