feat release: Add simple release script

Adds a simple script that will build stripped binaries for various platforms
and GPG-sign them.

.gitignore

@@ -1 +1,2 @@
 .idea/
+release/

README.md

@@ -74,7 +74,8 @@ to only update the `api` resource sets and the `frontend/user-page` resource set
 
 Assuming you have Go configured correctly, you can simply `go get github.com/tazjin/kontemplate/...`.
 
-There are signed binary releases available on the [releases page][] for Linux, OS X and Windows.
+There are signed binary releases available on the [releases page][] for Linux, OS X,
+FreeBSD and Windows.
 
 ## Usage
 

build-release.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+set -ueo pipefail
+
+readonly GIT_HASH="$(git rev-parse --short HEAD)"
+readonly LDFLAGS="-X main.gitHash=${GIT_HASH} -w -s"
+readonly VERSION="1.0-${GIT_HASH}"
+
+function build-for() {
+    local os="${1}"
+    local arch="${2}"
+    local target="release/${os}/${arch}"
+
+    echo "Building kontemplate for ${os}-${arch} in ${target}"
+
+    mkdir -p "${target}"
+
+    env GOOS="${os}" GOARCH="${arch}" go build \
+        -ldflags "${LDFLAGS}" \
+        -o "${target}/kontemplate" \
+        -tags netgo
+
+
+}
+
+function sign-for() {
+    local os="${1}"
+    local arch="${2}"
+    local target="release/${os}/${arch}"
+    local bin="${target}/kontemplate"
+    local hash="$(sha256sum ${bin})"
+    local tar="release/kontemplate-${VERSION}-${os}-${arch}.tar.gz"
+
+    echo "Signing kontemplate binary for ${os}-${arch} with SHA256 ${hash}"
+    gpg --sign "${bin}"
+
+    echo "Packing release into ${tar}"
+    tar czvf "${tar}" -C "${target}" kontemplate kontemplate.gpg
+}
+
+case "${1}" in
+    "build")
+        # Build releases for various operating systems:
+        build-for "linux" "amd64"
+        build-for "darwin" "amd64"
+        build-for "windows" "amd64"
+        build-for "freebsd" "amd64"
+        exit 0
+        ;;
+    "sign")
+        # Sign releases:
+        sign-for "linux" "amd64"
+        sign-for "darwin" "amd64"
+        sign-for "windows" "amd64"
+        sign-for "freebsd" "amd64"
+        exit 0
+        ;;
+esac