Can't checkout the same repo multiple times in a pipeline - yaml

Question

I have self-hosted agents on multiple environments that I am trying to run the same build/deploy processes on. I would like to be able to deploy the same code from a single repo to multiple systems concurrently. Thus, I have created an "overhead" pipeline, and several "processes" pipeline templates. Everything seems to be going very well, except for when I try to perform checkouts of the same repo twice in the same pipeline execution. I get the following error:
An error occurred while loading the YAML build pipeline. An item with the same key has already been added.
I would really like to be able to just click ONE button to trigger a main pipeline that calls all the templates requires and gives the parameters needed to get all my jobs done at once. I could of course define this "overhead" pipeline and then queue up as many instances as I need of it per systems that I need to deploy to, but I'm lazy, hence why I'm using pipelines!
As soon as I remove the checkout from Common.yml, the validation succeeds without any issues. If I keep the checkout in there but only call the Common.yml once for the entire Overhead pipeline, then it succeeds without any issues as well. But the problem is: I need to pull the contents of the repo to EACH of my agents that are running on completely separate environments that are in no way ever able to talk to each other (can't pull the information to one agent and have it do some sort of a "copy" to all the other agent locations.....).
Any assistance is very much welcomed, thank you!
The following is my "overhead" pipeline:
# azure-pipelines.yml
trigger:
none
parameters:
- name: vLAN
type: string
default: 851
values:
- 851
- 1105
stages:
- stage: vLAN851
condition: eq('${{ parameters.vLAN }}', '851')
pool:
name: xxxxx
demands:
- vLAN -equals 851
jobs:
- job: Common_851
steps:
- template: Procedures/Common.yml
- job: Export_851
dependsOn: Common_851
steps:
- template: Procedures/Export.yml
parameters:
Server: ABTS-01
- stage: vLAN1105
condition: eq('${{ parameters.vLAN }}', '1105')
pool:
name: xxxxx
demands:
- vLAN -equals 1105
jobs:
- job: Common_1105
steps:
- template: Procedures/Common.yml
- job: Export_1105
dependsOn: Common_1105
steps:
- template: Procedures/Export.yml
parameters:
Server: OTS-01
And here is the "Procedures/Common.yml":
steps:
- checkout: git://xxxxx/yyyyy#$(Build.SourceBranchName)
clean: true
enabled: true
timeoutInMinutes: 1
- task: UsePythonVersion#0
enabled: true
timeoutInMinutes: 1
displayName: Select correct version of Python
inputs:
versionSpec: '3.8'
addToPath: true
architecture: 'x64'
- task: CmdLine#2
enabled: true
timeoutInMinutes: 5
displayName: Ensure Python Requirements Installed
inputs:
script: |
python -m pip install GitPython
And here is the "Procedures/Export.yml":
parameters:
- name: Server
type: string
steps:
- task: PythonScript#0
enabled: true
timeoutInMinutes: 3
displayName: xxxxx
inputs:
arguments: --name "xxxxx" --mode True --Server ${{ parameters.Server }}
scriptSource: 'filePath'
scriptPath: 'xxxxx/main.py'

Answer 1

I managed to make checkout work with variable branch names by using template expression variables ${{ ... }} instead of macro syntax $(...) variables.
The difference is that, template expressions are processed at compile time while macros are processed at runtime.
So in my case I have something like:
- checkout: git://xxx/yyy#${{ variables.BRANCH_NAME }}
For more information about variables syntax :
Understand variable syntax

Answer 2

I couldn't get it to work with expressions but I was able to get it to work using repository resources following the documentation at: https://learn.microsoft.com/en-us/azure/devops/pipelines/repos/multi-repo-checkout?view=azure-devops
resources:
repositories:
- repository: MyGitHubRepo # The name used to reference this repository in the checkout step
type: git
name: MyAzureProjectName/MyGitRepo
ref: $(Build.SourceBranch)
trigger:
- main
pool:
vmImage: 'ubuntu-latest'
#some job
steps:
- checkout: MyGitHubRepo
#some other job
steps:
- checkout: MyGitHubRepo
- script: dir $(Build.SourcesDirectory)