I’m trying to build a docker in a pipeline

My project structure is as follow (locally)

path/to/project/
├─ ci/
│  ├─ dockerfiles/
│  │  ├─ build.dockerfile
│  ├─ configs/
│  │  ├─ config.json
│  ├─ scripts/
│  │  ├─ templates/
│  |  |  ├─ build.azure-pipeline.yml
│  │  ├─ azure-pipeline.yml
├─ src/

And in its Azure DevOps repo:

ci/
├─ dockerfiles/
│  ├─ build.dockerfile
├─ configs/
│  ├─ config.json
├─ scripts/
│  ├─ templates/
|  |  ├─ build.azure-pipeline.yml
│  ├─ azure-pipeline.yml
src/

The interesting parts of the files are as follow:

azure-pipeline.yml file:

pool:
  vmImage: ubuntu-latest
  
stages:
  - stage: Build
    jobs:
      - template: templates/build.azure-pipeline.yml
        parameters:
          ...

build.azure-pipeline.yml file:

parameters:
  ...

jobs:
- job: build_${{ parameters.build }}
  steps:
  - checkout: self
    submodules: recursive
    persistCredentials: true

  - task: DockerInstaller@0
    inputs:
      dockerVersion: '20.10.9'

  - task: Docker@2
    displayName: Build
    inputs:
      repository: 'repositories/project'
      command: 'build'
      Dockerfile: 'ci/dockerfiles/build.dockerfile'
      buildContext: '.'
      arguments: ...

build.dockerfile file:

FROM ubuntu:22.04 AS build-env
SHELL ["/bin/bash", "-lc"]

WORKDIR /app

COPY 'ci/configs/config.json' '/app/config.json'

I can build it, with no issue, locally with the following command:

docker buildx build 
    -f ~/path/to/project/ci/dockerfiles/build.dockerfile 
    --load ~/path/to/project

But when running the pipeline in Azure DevOps, it throws the following error:

##[error]#29 [build-env 25/26] COPY ci/configs/config.json /app/config.json
##[error]#29 sha256:f99004049a1f734d017dee2ba835634a67abb44913e4dcbb5b2293a877ccb33d
##[error]#29 ERROR: failed to calculate checksum of ref 68fa3e36-3e48-46b1-9ff3-248c6f3575df::h23it1x41ylkkv9vx2ydspezg: "/ci/configs/config.json": not found

And I have the same error for every COPY command, be it with files in the ci folder or src folder.

I thought the buildContext: '.' part of the build.azure-pipeline.yml file was the problem, so I tried with several other values '../../..' or '../..' to check if I had to put a relative path from the yml or dockerfile. I also tried with other values such as '$(Build.Repository.LocalPath)' but nothing seems to work.

The only difference I see between the local build and the one from Azure is when loading the context.

Locally, I have:

 => [internal] load .dockerignore
 => => transferring context: 2B
 => [build-env  1/26] FROM docker.io/library/ubuntu:22.04
 => [internal] load build context
 => => transferring context: 1.32MB    

And in Azure DevOps:

#3 [internal] load .dockerignore
#3 transferring context: 2B done
#3 DONE 0.0s

#18 [build-env  1/26] FROM docker.io/library/ubuntu:22.04
#18 DONE 0.0s

#5 [internal] load build context
#5 transferring context: 490.43kB 0.0s done
#5 DONE 0.1s

The Azure context is way smaller than the local one, I don’t know if it can explain the issue.

So here am I, asking, what did I do wrong ?