api: add initial implementation

The package parses constants from:

- tarantool/src/box/errcode.h
- tarantool/src/box/iproto_constants.h
- tarantool/src/box/iproto_features.h

You could to generate the code with the command:

TT_TAG=master make

Closes tarantool/go-tarantool#267

Author: oleg-jukovec

.github/workflows/test.yml

@@ -0,0 +1,91 @@
+name: testing
+
+on:
+  push:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  tests:
+    # We want to run on external PRs, but not on our own internal
+    # PRs as they'll be run by the push to the branch.
+    #
+    # The main trick is described here:
+    # https://github.com/Dart-Code/Dart-Code/pull/2375
+    #
+    # Also we want to run it always for manually triggered workflows.
+    if: (github.event_name == 'push') ||
+      (github.event_name == 'pull_request' &&
+        github.event.pull_request.head.repo.full_name != github.repository) ||
+      (github.event_name == 'workflow_dispatch')
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        golang:
+          - '1.13'
+          - '1.20'
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - name: Setup golang ${{ matrix.golang }}
+      uses: actions/setup-go@v3
+      with:
+        go-version: ${{ matrix.golang }}
+
+    - run: make test
+
+  master-build:
+    if: (github.event_name == 'push') ||
+      (github.event_name == 'pull_request' &&
+        github.event.pull_request.head.repo.full_name != github.repository) ||
+      (github.event_name == 'workflow_dispatch')
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - uses: actions/setup-go@v3
+
+    - run: echo "$(go env GOPATH)/bin" >> $GITHUB_PATH
+
+    - run: make deps
+
+    - run: TT_TAG=master make
+
+  golangci-lint:
+    if: (github.event_name == 'push') ||
+      (github.event_name == 'pull_request' &&
+        github.event.pull_request.head.repo.full_name != github.repository) ||
+      (github.event_name == 'workflow_dispatch')
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+
+    steps:
+    - uses: actions/checkout@v3
+
+    - uses: actions/setup-go@v3
+
+    - name: golangci-lint
+      uses: golangci/golangci-lint-action@v3
+      continue-on-error: true
+      with:
+        # The first run is for GitHub Actions error format.
+        args: -E goimports
+
+    - name: golangci-lint
+      uses: golangci/golangci-lint-action@v3
+      with:
+        # The second run is for human-readable error format with a file name
+        # and a line number.
+        args: --out-${NO_FUTURE}format colored-line-number -E goimports

Makefile

@@ -0,0 +1,23 @@
+SHELL := /bin/bash
+
+.PHONY: all
+all: generate test
+
+.PHONY: deps
+deps:
+	go install golang.org/x/tools/cmd/goimports@latest
+	go install golang.org/x/tools/cmd/stringer@latest
+
+.PHONY: format
+format:
+	goimports -l -w .
+
+.PHONY: generate
+generate:
+	go generate ./...
+
+.PHONY: test
+test:
+	@echo "Running all packages tests"
+	go clean -testcache
+	go test -tags ./... -v -p 1

README.md

@@ -0,0 +1,78 @@
+[![Go Reference][godoc-badge]][godoc-url]
+[![Actions Status][actions-badge]][actions-url]
+[![Telegram][telegram-badge]][telegram-url]
+[![Telegram Russian][telegram-badge]][telegramru-url]
+
+# iproto
+
+## Import
+
+```go
+import "github.com/tarantool/go-iproto"
+```
+
+## Overview
+
+Package `iproto` contains IPROTO constants.
+
+The code generated from Tarantool code. Code generation is only supported for
+an actual commit/release. We do not have a goal to support all versions of
+Tarantool with a code generator.
+
+## Example
+
+```go
+package main
+
+import (
+	"fmt"
+
+	"github.com/tarantool/go-iproto"
+)
+
+func main() {
+	fmt.Printf("%s=%d\n", iproto.ER_READONLY, iproto.ER_READONLY)
+	fmt.Printf("%s=%d\n", iproto.IPROTO_FEATURE_WATCHERS, iproto.IPROTO_FEATURE_WATCHERS)
+	fmt.Printf("%s=%d\n", iproto.IPROTO_FLAG_COMMIT, iproto.IPROTO_FLAG_COMMIT)
+	fmt.Printf("%s=%d\n", iproto.IPROTO_SYNC, iproto.IPROTO_SYNC)
+	fmt.Printf("%s=%d\n", iproto.IPROTO_SELECT, iproto.IPROTO_SELECT)
+}
+```
+
+## Development
+
+You need to install `git` and `go1.13+` first. After that, you need to install
+additional dependencies into `$GOBIN`:
+
+```bash
+make deps
+```
+
+You can generate the code with commands:
+
+```bash
+TT_TAG=master make
+TT_TAG=2.10.6 make
+TT_TAG=master TT_REPO=https://github.com/my/tarantool.git make
+```
+
+You need to specify a target branch/tag with the environment variable `TT_TAG`
+and you could to specify a repository with the `TT_REPO`.
+
+Makefile has additional targets that can be useful:
+
+```bash
+make format
+TT_TAG=master make generate
+make test
+```
+
+A good starting point is [generate.go](./generate.go).
+
+[actions-badge]: https://github.com/tarantool/go-iproto/actions/workflows/test.yml/badge.svg
+[actions-url]: https://github.com/tarantool/go-iproto/actions/workflows/test.yml
+[godoc-badge]: https://pkg.go.dev/badge/github.com/tarantool/go-iproto.svg
+[godoc-url]: https://pkg.go.dev/github.com/tarantool/go-iproto
+[telegram-badge]: https://img.shields.io/badge/Telegram-join%20chat-blue.svg
+[telegram-url]: http://telegram.me/tarantool
+[telegramru-url]: http://telegram.me/tarantoolru