Checkout part of a branch in Azure DevOps Pipeline

Question

My repository in my organisation's devops project contains a lot of .net solutions and some unity projects as well. When I run my build pipeline, it fails due to several of these:

Error MSB3491: Could not write lines to file "obj\Release\path\to\file". There is not enough space on the disk.

I would like the pipeline to only checkout and fetch parts of the repository that are required for a successful build. This might also help with execution time of the pipeline since it currently also fetches the whole of my unity projects with gigabytes of resources which takes forever.

I would like to spread my projects across multiple repositories but the admin won't give me more than the one I already have. It got a lot better when I configured git fetch as shallow (--depth=1) but I still get the error every now and then.

This is how I configured the checkout:

steps:
- checkout: self
  clean: true
  # shallow fetch
  fetchDepth: 1
  lfs: false
  submodules: false

The build is done using VSBuild@1 task.

I can't find a valid solution to my problem except for using multiple repositories, which is not an option right now.

Edit: Shayki Abramczyk's solution #1 works perfectly. Here is my full implementation.

GitSparseCheckout.yml:

parameters:
  access: ''
  repository: ''
  sourcePath: ''

steps:
- checkout: none

- task: CmdLine@2
  inputs:
    script: |
      ECHO ##[command] git init
      git init
      ECHO ##[command] git sparse-checkout: ${{ parameters.sourcePath }}
      git config core.sparsecheckout true
      echo ${{ parameters.sourcePath }} >> .git/info/sparse-checkout
      ECHO ##[command] git remote add origin https://${{ parameters.repository }}
      git remote add origin https://${{ parameters.access }}@${{ parameters.repository }}
      ECHO ##[command] git fetch --progress --verbose --depth=1 origin master
      git fetch --progress --verbose --depth=1 origin master
      ECHO ##[command] git pull --progress --verbose origin master
      git pull --progress --verbose origin master

Checkout is called like this (where template path has to be adjusted):

- template: ../steps/GitSparseCheckout.yml
  parameters:
    access: anything:<YOUR_PERSONAL_ACCESS_TOKEN>
    repository: dev.azure.com/organisation/project/_git/repository
    sourcePath: path/to/files/

Answer 1

In Azure DevOps you don't have option to get only part of the repository, but there is a workaround: Disable the "Get sources" step and get only the source you want by manually executing the according git commands in a script.

To disable the default "Get Sources" just specify none in the checkout statement:

- checkout: none

In the pipeline add a CMD/PowerShell task to get the sources manually with one of the following 2 options:

1. Get only part of the repo with git sparse-checkout. For example, get only the directories src_1 and src_2 within the test folder (lines starting with REM ### are just the usual batch comments):

- script: |
    REM ### this will create a 'root' directory for your repo and cd into it
    mkdir myRepo
    cd myRepo
    REM ### initialize Git in the current directory
    git init
    REM ### set Git sparsecheckout to TRUE
    git config core.sparsecheckout true
    REM ### write the directories that you want to pull to the .git/info/sparse-checkout file (without the root directory)
    REM ### you can add multiple directories with multiple lines
    echo test/src_1/ >> .git/info/sparse-checkout
    echo test/src_2/ >> .git/info/sparse-checkout
    REM ### fetch the remote repo using your access token
    git remote add -f origin https://[e-mail]/repo
    REM ### pull the files from the source branch of this build, using the build-in Azure DevOps variable for the branch name
    git pull origin $(Build.SourceBranch)
    displayName: 'Get only test/src_1 & test/src_2 directories'

Now in the builds task make myRepo the working directory. Fetching the remote repo using an access token is necessary, since using checkout: none will prevent your login credentials from being used. In the end of the pipeline you may want to add step to clean the myRepo directory.

2. Get parts of the repo with Azure DevOps Rest API (Git - Items - Get Items Batch).