使用 Github API 更新倉庫

0. 總覽

本文爲大家提供一種使用 GitHub API 更新 GitHub 倉庫的方法。通常我們會使用 Git 客戶端 Commit 然後 Push 到 GitHub，但 GitHub 爲我們提供了相關 API，在某些情況下可以直接通過 API 更新倉庫。

在此之前有一些前置知識點，你需要了解 git 的儲存原理。碰巧最近掘金有一篇很火的文章有提到相關知識。

使用 GitHub API 更新倉庫只需六步。雖然對於第一次接觸的新手來說可能會有點複雜，但是理清關係之後思路便會很清晰了。

獲取 Ref：Ref 指 Git 的引用。如果要發起 Commit，必須知道你的 Commit 要提交到什麼地方去（Commit 是一個接一個的鏈狀關係，所以需要知道上一個 Commit 的信息），這一步做的就是這件事。
獲取 Commit：用於獲取當前 Commit 的 tree 的 sha。
生成 Blob：相當於正常本地提交的 add 操作，可以參考這裏的解釋。
生成 Tree：構建一個新的 tree，把上一步生成的 Blob 放到合適的位置。這裏需要用到的參數 base_tree 就是來自第二步的 Commit 信息。
生成 Commit：提交你的 tree，這步跟正常 commit 很接近，不過要你手動找到此次提交的上一次提交，借哈希值把新的 Commit 接起來。
更新 Ref：使 master 的指針指到你最新提交的版本。

注意：訪問 POST 方法的接口必須帶 token，雖然 GET 可以不帶，但是會限制訪問頻率，所以建議都帶上。相關文檔：https://developer.github.com/v3/#authentication

1. 獲取 Ref

1.1 文檔地址

https://developer.github.com/v3/git/refs/#get-a-reference

1.2 請求地址

GET https://api.github.com/repos/ssshooter/test/git/refs/heads/master

1.3 返回數據

{
  "ref": "refs/heads/master",
  "node_id": "MDM6UmVmMTY0Nzk4NDczOm1hc3Rlcg==",
  "url": "https://api.github.com/repos/ssshooter/test/git/refs/heads/master",
  "object": {
    "sha": "cda66de943082033f4b761639df77728d7bca4f0",
    "type": "commit",
    "url": "https://api.github.com/repos/ssshooter/test/git/commits/cda66de943082033f4b761639df77728d7bca4f0"
  }
}

2. 獲取 Commit

2.1 文檔地址

https://developer.github.com/v3/git/commits/#get-a-commit

2.2 請求地址

GET https://api.github.com/repos/ssshooter/test/git/commits/cda66de943082033f4b761639df77728d7bca4f0

2.3 返回數據

{
  "sha": "cda66de943082033f4b761639df77728d7bca4f0",
  "node_id": "MDY6Q29tbWl0MTY0Nzk4NDczOmNkYTY2ZGU5NDMwODIwMzNmNGI3NjE2MzlkZjc3NzI4ZDdiY2E0ZjA=",
  "url": "https://api.github.com/repos/ssshooter/test/git/commits/cda66de943082033f4b761639df77728d7bca4f0",
  "html_url": "https://github.com/ssshooter/test/commit/cda66de943082033f4b761639df77728d7bca4f0",
  "author": {
    "name": "DeJavuJo",
    "email": "[email protected]",
    "date": "2019-01-09T06:02:07Z"
  },
  "committer": {
    "name": "GitHub",
    "email": "[email protected]",
    "date": "2019-01-09T06:02:07Z"
  },
  "tree": {
    "sha": "d7a57d28ace0db12773c7d70675f94a48da6421f",
    "url": "https://api.github.com/repos/ssshooter/test/git/trees/d7a57d28ace0db12773c7d70675f94a48da6421f"
  },
  "message": "Create readme.md",
  "parents": [
  ],
  "verification": {
    "verified": true,
    "reason": "valid",
    "signature": "-----BEGIN PGP SIGNATURE-----\n\nwsBcBAABCAAQBQJcNY5fCRBK7hj4Ov3rIwAAdHIIABh8I89hATqg1mSYtpx1aY\nJt/woDobMO7FGE5qXO0NNrCMqwF6mdPJOMMMZvVWF1ULTm8ZJ52GAh5xAnPMZEnQ\n8tTjj/Qc0eZCm5B1xO66rgx+7eKkeGUPJj5bX7Lf0i9Se70Ff0jaCdH94RgiSL2d\nclDLhNyM4u6AH//k7S3Ud1O6ezXd4+99381Xa331PDLhJttUAbRFRCThszbcxRUT\nPvyhPNvXB5ug4J+tAMaZJvZEaED0c1k2Yx1+TYkLvPjOlqXvqaDVpMZieluD5l+f\nu13NAoCnLfBe0Skak/8MxRDbMcJYNW78ll60HAa6jJtElD8Vkek8WoVAZ8p3iIE=\n=xI87\n-----END PGP SIGNATURE-----\n",
    "payload": "tree d7a57d28ace0db12773c7d70675f94a48da6421f\nauthor DeJavuJo  1547013727 +0800\ncommitter GitHub  1547013727 +0800\n\nCreate readme.md"
  }
}

3. 生成 Blob

3.1 文檔地址

https://developer.github.com/v3/git/blobs/#create-a-blob

3.2 請求地址

POST https://api.github.com/repos/ssshooter/test/git/blobs

3.3 請求參數

{
  "content": "Content of the blob",
  "encoding": "utf-8"
}

3.4 返回數據

{
    "sha": "929246f65aab4d636cb229c790f966afc332c124",
    "url": "https://api.github.com/repos/ssshooter/test/git/blobs/929246f65aab4d636cb229c790f966afc332c124"
}

4. 生成 tree

4.1 文檔地址

https://developer.github.com/v3/git/trees/#create-a-tree

4.2 請求地址

POST https://api.github.com/repos/ssshooter/test/git/trees

4.3 請求參數

注意：tree.path 可以寫深層目錄，如 deep/deep/newFile.md（前面不用寫斜槓）

{
  "base_tree": "d7a57d28ace0db12773c7d70675f94a48da6421f", // commit tree 的 sha
  "tree": [
    {
      "path": "apiCommitFile.md", // 文件路徑
      "mode": "100644", // 類型，詳情看文檔
      "type": "blob",
      "sha": "929246f65aab4d636cb229c790f966afc332c124" // 剛纔生成的 blob 的 sha
    }
  ]
}

4.4 返回數據

{
    "sha": "2b3a65095ceb7cf4425f52d59ca5974d826cff80",
    "url": "https://api.github.com/repos/ssshooter/test/git/trees/2b3a65095ceb7cf4425f52d59ca5974d826cff80",
    "tree": [
        {
            "path": "readme.md",
            "mode": "100644",
            "type": "blob",
            "sha": "b1b716105590454bfc4c0247f193a04088f39c7f",
            "size": 5,
            "url": "https://api.github.com/repos/ssshooter/test/git/blobs/b1b716105590454bfc4c0247f193a04088f39c7f"
        },
        {
            "path": "tree",
            "mode": "040000",
            "type": "tree",
            "sha": "91d8d59147e395effaeacd01c9d8553b37cf77c5",
            "url": "https://api.github.com/repos/ssshooter/test/git/trees/91d8d59147e395effaeacd01c9d8553b37cf77c5"
        }
    ],
    "truncated": false
}

5. 生成 Commit

5.1 文檔地址

https://developer.github.com/v3/git/commits/#create-a-commit

5.2 請求地址

POST https://api.github.com/repos/ssshooter/test/git/commits

5.3 請求參數

{
  "message": "a Commit with GitHub api",
  "parents": [
    "cda66de943082033f4b761639df77728d7bca4f0" // 上次 commit 的sha
  ],
  "tree": "2b3a65095ceb7cf4425f52d59ca5974d826cff80"
}

5.4 返回數據

{
    "sha": "45c58a9358b67fc81e4034cb36c5196d791686ef",
    "node_id": "MDY6Q29tbWl0MTY0Nzk4NDczOjQ1YzU4YTkzNThiNjdmYzgxZTQwMzRjYjM2YzUxOTZkNzkxNjg2ZWY=",
    "url": "https://api.github.com/repos/ssshooter/test/git/commits/45c58a9358b67fc81e4034cb36c5196d791686ef",
    "html_url": "https://github.com/ssshooter/test/commit/45c58a9358b67fc81e4034cb36c5196d791686ef",
    "author": {
        "name": "ssshooter",
        "email": "[email protected]",
        "date": "2019-01-09T10:24:10Z"
    },
    "committer": {
        "name": "ssshooter",
        "email": "[email protected]",
        "date": "2019-01-09T10:24:10Z"
    },
    "tree": {
        "sha": "2b3a65095ceb7cf4425f52d59ca5974d826cff80",
        "url": "https://api.github.com/repos/ssshooter/test/git/trees/2b3a65095ceb7cf4425f52d59ca5974d826cff80"
    },
    "message": "a Commit with GitHub api",
    "parents": [
        {
            "sha": "cda66de943082033f4b761639df77728d7bca4f0",
            "url": "https://api.github.com/repos/ssshooter/test/git/commits/cda66de943082033f4b761639df77728d7bca4f0",
            "html_url": "https://github.com/ssshooter/test/commit/cda66de943082033f4b761639df77728d7bca4f0"
        }
    ],
    "verification": {
        "verified": false,
        "reason": "unsigned",
        "signature": null,
        "payload": null
    }
}

6. 更新 Ref

6.1 文檔地址

https://developer.github.com/v3/git/refs/#update-a-reference

6.2 請求地址

https://api.github.com/repos/ssshooter/test/git/refs/heads/master

6.3 請求參數

{
    "sha":"45c58a9358b67fc81e4034cb36c5196d791686ef",
    "force":true
}

6.4 返回數據

{
    "ref": "refs/heads/master",
    "node_id": "MDM6UmVmMTY0Nzk4NDczOm1hc3Rlcg==",
    "url": "https://api.github.com/repos/ssshooter/test/git/refs/heads/master",
    "object": {
        "sha": "45c58a9358b67fc81e4034cb36c5196d791686ef",
        "type": "commit",
        "url": "https://api.github.com/repos/ssshooter/test/git/commits/45c58a9358b67fc81e4034cb36c5196d791686ef"
    }
}

7. node.js 實踐代碼

var updateGitHubRes = function(blob, path) {
  var commitSha
  var commitTreeSha
  return getRef()
    .then(({ data }) => {
      commitSha = data.object.sha
      return getCommit(commitSha)
    })
    .then(({ data }) => {
      commitTreeSha = data.tree.sha
      return createBlob(blob)
    })
    .then(({ data }) => {
      var blobSha = data.sha
      return createTree(commitTreeSha, path, blobSha)
    })
    .then(({ data }) => {
      var treeSha = data.sha
      return createCommit(commitSha, treeSha)
    })
    .then(({ data }) => {
      var newCommitSha = data.sha
      return updataRef(newCommitSha)
    })
    .catch(err => {
      console.log(err)
    })
}

var getRef = function() {
  return axios.get(`/${owner}/${repo}/git/refs/heads/master`)
}

var getCommit = function(commitSha) {
  return axios.get(`/${owner}/${repo}/git/commits/${commitSha}`)
}

var createBlob = function(content) {
  return axios.post(`/${owner}/${repo}/git/blobs`, {
    content,
    encoding: 'utf-8'
  })
}

var createTree = function(base_tree, path, sha) {
  return axios.post(`/${owner}/${repo}/git/trees`, {
    base_tree, // commit tree 的 sha
    tree: [
      {
        path, // 文件路徑
        mode: '100644', // 類型，詳情看文檔
        type: 'blob',
        sha // 剛纔生成的 blob 的 sha
      }
    ]
  })
}

var createCommit = function(parentCommitSha, tree, message = 'update post') {
  return axios.post(`/${owner}/${repo}/git/commits`, {
    message,
    parents: [parentCommitSha],// 上次 commit 的sha
    tree
  })
}

var updataRef = function(newCommitSha) {
  return axios.post(`/${owner}/${repo}/git/refs/heads/master`, {
    sha: newCommitSha,
    force: true
  })
}

參考文獻

https://int128.hatenablog.com/entry/2017/09/05/161641
https://juejin.im/post/5c33f49de51d45523070f7bb
https://git-scm.com/book/zh/v2/Git-內部原理-Git-引用