Cannot trigger build via push to another repository in a YML Pipeline - azure-devops

Question

I have the following repositories:
my-app-repo - Contains the code for the app
pipeline-repo - A collection of pipelines that build my-app-repo as well as others
I'm trying to build a yml pipeline within pipeline-repo that will be triggered on a commit to my-app-repo.
According to the official yml documentation, it sounds possible but I'm not able to get it working.
Here's what I've tried:
pipeline-repo/my-app-repo-build.yml
resources:
repositories:
- repository: target_repo
type: git
name: my-project/my-app_repo
trigger:
branches:
include:
- master
jobs:
- job:
steps:
- script: echo "Should be triggered from a push to my-app-repo!"
The build is not triggering when I push to my-app-repo. It only kicks off for commits to the source repo (pipeline-repo) which I cannot change since that holds the yml definition.
Am I missing something easy?

Answer 1

Edit:
I see you've added an issue to the github repository you mentioned. I agree that it seems to be broken.
While you aren't exactly trying to provide template functionality to your pipelines, you might use it as a work around until the issue you created is addressed.
I've tested this in my playground and it seems to work.
In the app repository
resources:
repositories:
- repository: templates
type: git
name: Pipeline-Templates
trigger:
branches:
include:
- master
jobs:
- template: azure-pipelines-template.yml#templates
In the pipelines repository
jobs:
- job: Get_Last_10_Commits
pool:
vmImage: 'vs2017-win2016'
steps:
- task: PowerShell#2
inputs:
targetType: 'inline'
script: |
cd $(Build.SourcesDirectory)
Write-Host "Show git log (last 10):"
git log --oneline -10
One "advantage" of this work around is that you no longer need to specify that the repository to checkout is the resource repository and not the self (your template-repository) as the self repository is the app-repo.
This would allow you to restrict changes to the pipeline core by having it in a separate repo like you want, but would still trigger on the app-repo master.
Not ideal b/c you now have 2x .yml files for each build you need, but that's basically the definition of work around: not ideal.
It looks like your include syntax is wrong. Have you tried to use the simple syntax?
All of the examples (and my experience) show that you should use the wildcard syntax when your trigger has an include or exclude specification.
resources:
repositories:
- repository: myPHPApp
type: GitHub
connection: myGitHubConnection
source: ashokirla/phpApp
trigger:
branches:
include:
- features/*
exclude:
- features/experimental/*
paths:
exclude:
- README.md