Added presubmit script distilled from that in trillian (#29)

Removed some of the flags and branches that weren't needed, such as code
generation. This isn't hooked into CI _yet_, but at least developers can
run `./scripts/presubmit.sh` before submitting in the meantime.

scripts/check_license.sh

@@ -0,0 +1,46 @@
+#!/bin/bash
+#
+# Checks that source files (.go and .proto) have the Apache License header.
+# Automatically skips generated files.
+set -eu
+
+check_license() {
+  local path="$1"
+
+  if head -1 "$path" | grep -iq 'generated by'; then
+    return 0
+  fi
+
+  # Look for "Apache License" on the file header
+  if ! head -10 "$path" | grep -q 'Apache License'; then
+    # Format: $path:$line:$message
+    echo "$path:10:license header not found"
+    return 1
+  fi
+}
+
+main() {
+  if [[ $# -lt 1 ]]; then
+    echo "Usage: $0 <path>"
+    exit 1
+  fi
+
+  local code=0
+  while [[ $# -gt 0 ]]; do
+    local path="$1"
+    if [[ -d "$path" ]]; then
+      for f in "$path"/*.{go,proto}; do
+        if [[ ! -f "$f" ]]; then
+          continue  # Empty glob
+        fi
+        check_license "$f" || code=1
+      done
+    else
+      check_license "$path" || code=1
+    fi
+    shift
+  done
+  exit $code
+}
+
+main "$@"

scripts/presubmit.sh

@@ -0,0 +1,115 @@
+#!/bin/bash
+#
+# Presubmit checks for this repository.
+#
+# Checks for lint errors, spelling, licensing, correct builds / tests and so on.
+# Flags may be specified to allow suppressing of checks or automatic fixes, try
+# `scripts/presubmit.sh --help` for details.
+#
+# Globals:
+#   GO_TEST_TIMEOUT: timeout for 'go test'. Optional (defaults to 5m).
+set -eu
+
+check_pkg() {
+  local cmd="$1"
+  local pkg="$2"
+  check_cmd "$cmd" "try running 'go get -u $pkg'"
+}
+
+check_cmd() {
+  local cmd="$1"
+  local msg="$2"
+  if ! type -p "${cmd}" > /dev/null; then
+    echo "${cmd} not found, ${msg}"
+    return 1
+  fi
+}
+
+usage() {
+  echo "$0 [--coverage] [--fix] [--no-mod-tidy] [--no-build] [--no-linters]"
+}
+
+main() {
+  local coverage=0
+  local fix=0
+  local run_mod_tidy=1
+  local run_build=1
+  local run_lint=1
+  while [[ $# -gt 0 ]]; do
+    case "$1" in
+      --coverage)
+        coverage=1
+        ;;
+      --fix)
+        fix=1
+        ;;
+      --no-mod-tidy)
+        run_mod_tidy=0
+        ;;
+      --help)
+        usage
+        exit 0
+        ;;
+      --no-build)
+        run_build=0
+        ;;
+      --no-linters)
+        run_lint=0
+        ;;
+      *)
+        usage
+        exit 1
+        ;;
+    esac
+    shift 1
+  done
+
+  cd "$(dirname "$0")"  # at scripts/
+  cd ..  # at top level
+
+  go_srcs="$(find . -name '*.go' | \
+    grep -v mock_ | \
+    grep -v .pb.go | \
+    grep -v _string.go | \
+    grep -v .shims.go | \
+    tr '\n' ' ')"
+
+  if [[ "$fix" -eq 1 ]]; then
+    check_pkg goimports golang.org/x/tools/cmd/goimports || exit 1
+
+    echo 'running gofmt'
+    gofmt -s -w ${go_srcs}
+    echo 'running goimports'
+    goimports -w ${go_srcs}
+    if [[ "$run_mod_tidy" -eq 1 ]]; then
+      echo 'running go mod tidy'
+      go mod tidy
+    fi
+  fi
+
+  if [[ "${run_build}" -eq 1 ]]; then
+    echo 'running go build'
+    go build ./...
+
+    export TEST_FLAGS="-timeout=${GO_TEST_TIMEOUT:-5m}"
+
+    if [[ ${coverage} -eq 1 ]]; then
+      TEST_FLAGS+=" -covermode=atomic -coverprofile=coverage.txt"
+    fi
+
+    echo "running go test ${TEST_FLAGS} ./..."
+    go test ${TEST_FLAGS} ./...
+  fi
+
+  if [[ "${run_lint}" -eq 1 ]]; then
+    check_cmd golangci-lint \
+      'have you installed github.com/golangci/golangci-lint?' || exit 1
+
+    echo 'running golangci-lint'
+    golangci-lint run --deadline=8m
+    echo 'checking license headers'
+    ./scripts/check_license.sh ${go_srcs}
+  fi
+}
+
+main "$@"