Managing your git repository via REST API in VSTS

Let's say you'd like to store some results of a build or a release inside a repository. It could be

Let's say you'd like to store some results of a build or a release inside a repository. It could be any reason - easy access, versioning, the only tool you have access to. By default VSTS doesn't provide any kind of git-related steps, which could be helpful in such case. Fortunately, once more its REST API comes to the rescue, giving us an opportunity to fully manage repositories with the possibility to push multiple commits.

Before we start, take a look at the overview to understand what are the general capabilities of this API.

Making an initial commit

Once you have your git repository created in VSTS, you can either initialize it with a commit from the GUI or push an initial commit using API. If you take a look at the example from the documentation:

/
POST /_apis/git/repositories/{repository}/pushes?api-version={version}

and its body:

/
{
  "refUpdates": [
    {
      "name": "refs/heads/master",
      "oldObjectId": "0000000000000000000000000000000000000000"
    }
  ],
  "commits": [
    {
      "comment": "Initial commit.",
      "changes": [
        {
          "changeType": "add",
          "item": {
            "path": "/readme.md"
          },
          "newContent": {
            "content": "My first file!",
            "contentType": "rawtext"
          }
        }
      ]
    }
  ]
}

you'll see mostly self-descriptive properties, which build this JSON. The only thing - oldObjectId - is not so obvious. Basically it's SHA1 of the commit this commit is based on - since there're no commits yet, it's basicaly a string full of zeros.

Pushing data

Making an initial commit is a piecie of cake. What if we'd like to update an existing file? The main issue here is to find an oldObjectId, which is required to actually make a request successful. Once more the API becomes handy here - what we can do is to fetch a list list of all pushes and take the last one. Take a look at the signature from the documentation:

/
GET https://{instance}/DefaultCollection/_apis/git/repositories/{repository}/pushes?api-version={version}[&fromDate={dateTime}&toDate={dateTime}&pusherId={guid}&$skip={integer}&$top={integer}]

What is great about this request is the possibility to filter the data - we don't have to download all pushes, only those from the date interval, made by a specific pusher or maybe only the top N. The response gives us a list of pushes ordered from the newest to the oldest. That is important here is to pass includeRefUpdates=true parameter in the query string. This way we'll get following additional property in the response:

/
{
          "repositoryId": "04baf35b-faec-4619-9e42-ce2d0ccafa4c",
          "name": "refs/heads/master",
          "oldObjectId": "0000000000000000000000000000000000000000",
          "newObjectId": "5e108508e2151f5513fffaf47f3377eb6e571b20"
}

and we're able to refer to the newObjectId property to make an update. Once we have it, we can use once more the endpoint used to create an initial commit with a slightly modified body:

/
{
  "refUpdates": [
    {
      "name": "refs/heads/master",
      "oldObjectId": "5e108508e2151f5513fffaf47f3377eb6e571b20"
    }
  ],
  "commits": [
    {
      "comment": "Added a few more items to the task list.",
      "changes": [
        {
          "changeType": "edit",
          "item": {
            "path": "/readme.md"
          },
          "newContent": {
            "content": "Modified readme file!",
            "contentType": "rawtext"
          }
        }
      ]
    }
  ]
}

Once we post this request, a new commit should be pushed and visible when you access a repository.

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