为了解决这个问题，需要指定trigger为"none"，然后在step中添加自定义脚本来实现触发操作。示例代码如下：

trigger:
  branches:
    include:
    - master 
  paths:
    include:
    - /src/*
    exclude:
    - /src/tests/*

steps:
- script: echo The build was triggered manually. 
  condition: eq(variables['Build.Reason'], 'Manual')
- script: echo The build was triggered by a Git push. 
  condition: eq(variables['Build.Reason'], 'Push')
- script: echo The build was triggered by a Git PR. 
  condition: eq(variables['Build.Reason'], 'PullRequest')
- script: echo Add custom conditions here. 
  condition: eq(variables['Build.Reason'], 'none')

通过这种方式，你可以在pipeline中自定义触发条件，并避免pipeline在推送或者合并代码时随机触发。