How to create a new build or release using the API and YAML - azure-devops

Question

I'm just looking for direction here as, possibly, the api already does this and I'm misunderstanding / can't find the right resource.
What I would like to do is to be able to call the azure-devops api to create a new build definition for me when I supply it with all the necessary yaml files for each stage.
I expected a create endpoint which would take in a few basic pieces of information to create the build / release definition then a collection of yaml files to create the tasks.
I've found Create your first pipeline and Api 5.0 BuildDefinition/Create however neither of these mention posting a yaml definition to the api. I was expecting far less items in the request body considering the yaml definitions contain most of the information required.
Does the api support this? Will it ever support this?

Answer 1

There is no docs for Rest Api with yaml, but if you try to get an existing yaml definition you`ll meet the next example:
So if you want to edit the process you have to edit existing yaml file. If you want create/clone an existing build definition you may try to create/clone yaml file and post a request (Definitions - Create) with the process member:
yamlFilename = path to yaml file in the repository
type = 2
This powershell example to clone a build definition with yaml:
$pat = '{personal access token}'
$base64AuthInfo = [System.Convert]::ToBase64String([System.Text.Encoding]::UTF8.GetBytes(":$pat"))
$uri = 'https://dev.azure.com/{organization}/{team_project}/_apis/build/definitions/{buil_id}?api-version=5.0'
$result = Invoke-RestMethod -Method Get -Uri $uri -Headers #{Authorization=("Basic {0}" -f $base64AuthInfo)} -ErrorAction Stop
$body = $result | ConvertTo-Json -Depth 7
$existingyaml = '"yamlFilename": "{path to yaml for existing buildef}"'
$newyaml = '"yamlFilename": "{path to new yaml}"'
$buildname = '"name": "{existing build name}"'
$newbuildname = '"name": "{new build name}"'
$body = $body.Replace($existingyaml, $newyaml)
$body = $body.Replace($buildname, $newbuildname)
$Uri = "https://dev.azure.com/{organization}/{team_project}/_apis/build/definitions?api-version=5.0"
$newBuildDef = Invoke-RestMethod -Uri $Uri -Headers #{Authorization=("Basic {0}" -f $base64AuthInfo)} -Method Post -Body $body -ContentType "application/json" -ErrorAction Stop

Answer 2

Yes, you are right, you could do a get on a build using the api, and change the variables, it should work.
If you only need to modify variables, you could use variable group to store values, then you can get the variable group and modify the variable values using the Variablegroups api.