Self-Update Mechanism for Go Commands using GitHub
==================================================

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[go-github-selfupdate][] is a Go library to provide self-update mechanism to command line tools.

Go does not provide the way to install/update the stable version of tools. By default, Go command line tools are updated

- using `go get -u` (updating to HEAD)
- using system's package manager (depending on the platform)
- downloading executables from GitHub release page manually

By using this library, you will get 4th choice:

- from your command line tool directly (and automatically)

go-github-selfupdate detects the information of the latest release via [GitHub Releases API][] and check the current version.
If newer version than itself is detected, it downloads released binary from GitHub and replaces itself.

- Automatically detects the latest version of released binary on GitHub
- Retrieve the proper binary for the OS and arch where the binary is running
- Update the binary with rollback support on failure
- Tested on Linux, macOS and Windows (using Travis CI and AppVeyor)
- Many archive and compression formats are supported (zip, gzip, tar)

And small wrapper CLI is provided:

- [detect-latest-release](./cmd/detect-latest-release): Detect the latest release of given GitHub repository from command line

[go-github-selfupdate]: https://github.com/rhysd/go-github-selfupdate
[GitHub Releases API]: https://developer.github.com/v3/repos/releases/

## Try Out Example

Example to understand what this library does is prepared as [CLI](./cmd/selfupdate-example/main.go).

Install it at first.

```
$ go get -u github.com/rhysd/go-github-selfupdate/tree/master/cmd/selfupdate-example
```

And check the version by `-version`. `-help` flag is also available to know all flags.

```
$ selfupdate-example -version
```

It should show `v1.2.3`.

Then run `-selfupdate`

```
$ selfupdate-example -selfupdate
```

It should replace itself and finally shows a message containing release notes.

Please check the binary version is updated to `v1.2.4` with `-version`. The binary is up-to-date. So running `-selfupdate` again only shows 'Current binary is the latest version'.

### Real World Examples

Following tools are using this library.

- [dot-github](https://github.com/rhysd/dot-github)
- [dotfiles](https://github.com/rhysd/dotfiles)
- [git-clone-all](https://github.com/rhysd/git-clone-all)

## Usage

### Code Usage

It provides `selfupdate` package.

- `selfupdate.UpdateSelf()`: Detect the latest version of itself and run self update.
- `selfupdate.UpdateCommand()`: Detect the latest version of given repository and update given command.
- `selfupdate.DetectLatest()`: Detect the latest version of given repository.
- `selfupdate.UpdateTo()`: Update given command to the binary hosted on given URL.

Following is the easiest way to use this package.

```go
import (
    "log"
    "github.com/blang/semver"
    "github.com/rhysd/go-github-selfupdate/selfupdate"
)

const version = "1.2.3"

func doSelfUpdate() {
    v := semver.MustParse(version)
    latest, err := selfupdate.UpdateSelf(v, "myname/myrepo")
    if err != nil {
        log.Println("Binary update failed:", err)
        return
    }
    if latest.Version.Equals(v) {
        // latest version is the same as current version. It means current binary is up to date.
        log.Println("Current binary is the latest version", version)
    } else {
        log.Println("Successfully updated to version", latest.Version)
        log.Println("Release note:\n", latest.ReleaseNotes)
    }
}
```

Following asks user to update or not.

```go
import (
    "bufio"
    "github.com/blang/semver"
    "github.com/rhysd/go-github-selfupdate/selfupdate"
    "log"
    "os"
)

const version = "1.2.3"

func confirmAndSelfUpdate() {
    latest, found, err := selfupdate.DetectLatest("owner/repo")
    if err != nil {
        log.Println("Error occurred while detecting version:", err)
        return
    }

    v := semver.MustParse(version)
    if !found || latest.Version.Equals(v) {
        log.Println("Current version is the latest")
        return
    }

    fmt.Print("Do you want to update to", latest.Version, "? (y/n): ")
    input, err := bufio.NewReader(os.Stdin).ReadString('\n')
    if err != nil || (input != "y\n" && input != "n\n") {
        log.Println("Invalid input")
        return
    }
    if input == "n\n" {
        return
    }

    if err := selfupdate.UpdateTo(latest.AssetURL, os.Args[0]); err != nil {
        log.Println("Error occurred while updating binary:", err)
        return
    }
    log.Println("Successfully updated to version", latest.Version)
}
```

Please see [the documentation page][GoDoc] for more detail.

### Naming Rules of Released Binaries

go-github-selfupdate assumes that released binaries are put for each combination of platforms and archs.
Binaries for each platform can be easily built using tools like [gox][]

You need to put the binaries with the following format.

```
{cmd}_{goos}_{goarch}{.ext}
```

`{cmd}` is a name of command.
`{goos}` and `{goarch}` are the platform and the arch type of the binary.
`{.ext}` is a file extension. go-github-selfupdate supports `.zip`, `.gzip` and `.tar.gz`.
You can also use blank and it means binary is not compressed.

If you compress binary, uncompressed directory or file must contain the executable named `{cmd}`. 

And you can also use `-` for separator instead of `_` if you like.

For example, if your command name is `foo-bar`, one of followings is expected to be put in release
page on GitHub as binary for platform `linux` and arch `amd64`.

- `foo-bar_linux_amd64` (executable)
- `foo-bar_linux_amd64.zip` (zip file containing `foo-bar`)
- `foo-bar_linux_amd64.tar.gz` (tar file containing `foo-bar`)
- `foo-bar_linux_amd64.gzip` (gzip file of the executable `foo-bar`)
- `foo-bar-linux-amd64.tar.gz` (`-` is also ok for separator)

To archive the executable directly on Windows, `.exe` can be added before file extension like
`foo-bar_windows_amd64.exe.zip`.

[gox]: https://github.com/mitchellh/gox


### Naming Rules of Versions (=Git Tags)

go-github-selfupdate searches binaries' versions via Git tag names (not a release title).
When your tool's version is `1.2.3`, you should use the version number for tag of the Git
repository (i.e. `1.2.3` or `v1.2.3`).

This library assumes you adopt [semantic versioning][]. It is necessary for comparing versions
systematically.

Prefix before version number `\d+\.\d+\.\d+` is automatically omitted. For example, `ver1.2.3` or
`release-1.2.3` are also ok.

Tags which don't contain a version number are ignored (i.e. `nightly`). And releases marked as `pre-release`
are also ignored.

[semantic versioning]: https://semver.org/


### Structure of Releases

In summary, structure of releases on GitHub looks like:

- `v1.2.0`
  - `foo-bar-linux-amd64.tar.gz`
  - `foo-bar-linux-386.tar.gz`
  - `foo-bar-darwin-amd64.tar.gz`
  - `foo-bar-windows-amd64.zip`
  - ... (Other binaries for v1.2.0)
- `v1.1.3`
  - `foo-bar-linux-amd64.tar.gz`
  - `foo-bar-linux-386.tar.gz`
  - `foo-bar-darwin-amd64.tar.gz`
  - `foo-bar-windows-amd64.zip`
  - ... (Other binaries for v1.1.3)
- ... (older versions)

Tags which don't contain a version number are ignored (i.e. `nightly`). And releases marked as `pre-release` are also ignored.

### Debugging

This library can output logs for debugging. By default, logger is disabled.
You can enable the logger by following and can know the details of the self update.

```go
selfupdate.EnableLog()
```

## Dependencies

This library utilizes [go-github][] to retrieve the information of releases and [go-update][] to replace
current binary and [semver][] to compare versions.

> Copyright (c) 2013 The go-github AUTHORS. All rights reserved.

> Copyright 2015 Alan Shreve

> Copyright (c) 2014 Benedikt Lang <github at benediktlang.de>

[go-github]: https://github.com/google/go-github
[go-update]: https://github.com/inconshreveable/go-update
[semver]: https://github.com/blang/semver

## What is the different from [tj/go-update][]?

This library goal is the same as tj/go-update, but it's different in following points.

tj/go-update:

- does not support Windows
- only allows `v` for version prefix
- does not ignore pre-release
- has [only a few tests](https://github.com/tj/go-update/blob/master/update_test.go)

[tj/go-update]: https://github.com/tj/go-update

## License

Distributed under the [MIT License](LICENSE)

[GoDoc Badge]: https://godoc.org/github.com/rhysd/go-github-selfupdate/selfupdate?status.svg
[GoDoc]: https://godoc.org/github.com/rhysd/go-github-selfupdate/selfupdate
[TravisCI Status]: https://travis-ci.org/rhysd/go-github-selfupdate.svg?branch=master
[TravisCI]: https://travis-ci.org/rhysd/go-github-selfupdate
[AppVeyor Status]: https://ci.appveyor.com/api/projects/status/1tpyd9q9tw3ime5u/branch/master?svg=true
[AppVeyor]: https://ci.appveyor.com/project/rhysd/go-github-selfupdate/branch/master
[Codecov Status]: https://codecov.io/gh/rhysd/go-github-selfupdate/branch/master/graph/badge.svg
[Codecov]: https://codecov.io/gh/rhysd/go-github-selfupdate