在AWS CodePipeline中，每个阶段都会有一个或多个操作（actions）。而每个操作都可以使用不同的AWS服务来完成任务，其中包括S3、CodeCommit、CodeBuild等。

要在CodePipeline中添加两个依次执行的源阶段，可以参考以下步骤：

1. 创建一个包含两个阶段的CodePipeline流水线，并配置源（source）阶段和第一个构建（build）阶段。

---
Resources:
  SourceRepository:
    Type: AWS::CodeCommit::Repository
    Properties:
      RepositoryName: !Sub ${ProjectName}-repository
 
  BuildProject:
    Type: AWS::CodeBuild::Project
    Properties:
      Name: !Sub ${ProjectName}-build
      ServiceRole: !GetAtt CodeBuildServiceRole.Arn
      Source:
        Type: CODEPIPELINE
      Environment:
        ComputeType: BUILD_GENERAL1_SMALL
        Image: aws/codebuild/amazonlinux2-x86_64-standard:3.0
        Type: LINUX_CONTAINER
      Artifacts:
        Type: CODEPIPELINE

2. 接下来，在CodePipeline流水线中添加第二个源（source）阶段，以在每个阶段之间添加一个源步骤。

---
Resources:
  SourceRepository1:
    Type: AWS::CodeCommit::Repository
    Properties:
      RepositoryName: !Sub ${ProjectName}-repository-1
 
  SourceRepository2:
    Type: AWS::CodeCommit::Repository
    Properties:
      RepositoryName: !Sub ${ProjectName}-repository-2
 
  BuildProject:
    Type: AWS::CodeBuild::Project
    Properties:
      Name: !Sub ${ProjectName}-build-project
      ServiceRole: !GetAtt CodeBuildServiceRole.Arn
      Source:
        Type: CODEPIPELINE
      Environment:
        ComputeType: BUILD_GENERAL1_SMALL
        Image: aws/codebuild/amazonlinux2-x86_64-standard:3.0
        Type: LINUX_CONTAINER
      Artifacts:
        Type: CODEPIPELINE
 
  Pipeline:
    Type: AWS::CodePipeline::Pipeline
    Properties:
      Name: !Sub ${ProjectName}-pipeline
      RoleArn: !GetAtt CodePipelineServiceRole.Arn
      Stages:
      - Name: Source1
        Actions:
        - Name: Source1RepoAction
          ActionTypeId:
            Category: Source
            Owner: AWS
            Version: '1'
            Provider: CodeCommit
          OutputArtifacts:
          -