Support glob/multiple Cobertura files (or action-side merge) in the file input

该 issue 没有指出任何仓库文件或测试。首先定位必需的 file 输入的实现和上传路径，然后确定 glob、列表或目录输入以及 Cobertura 合并应如何适配；当矩阵和单仓库多项目报告可以在不单独执行合并步骤的情况下上传，或聚合行为已有文档说明时，即可视为完成。

Summary

The file input accepts a single Cobertura XML report. Projects with a test matrix or monorepo layout produce many per-project Cobertura files, so they must be merged into one file before this action can consume them. It would help if the action accepted multiple files / a glob / a directory and merged them itself.

Current behavior

• file is a single, required path to one Cobertura XML report.
• There is no glob, multi-file, or directory input.

Desired behavior

Accept any one of:

• glob patterns in file (e.g. **/*.cobertura.xml), or
• a files input taking a newline- or comma-separated list, or
• a directory + pattern,

and merge the matched reports (action-side or server-side) before upload. For comparison, codecov/codecov-action accepts multiple files / directory search, so matrix and monorepo setups upload without a separate merge step.

Use case

We're migrating a public .NET OSS monorepo (ChilliCream/graphql-platform) from Codecov to GitHub Code Quality. CI runs a 125-project test matrix, and each job emits its own *.cobertura.xml artifact. Codecov merged them server-side. With this action we now add an explicit merge step first:

- run: dotnet tool install --global dotnet-coverage
- run: >
    dotnet-coverage merge
    --output merged.cobertura.xml
    --output-format cobertura
    "**/*.cobertura.xml"
- uses: actions/upload-code-coverage@v1
  with:
    file: merged.cobertura.xml
    language: "C#"
    label: code-coverage/dotnet

This works, but native multi-file/glob support (or an action-side merge) would remove the extra tooling and step for the common matrix/monorepo case.

Question

If multiple uploads with distinct labels are made (e.g. one per matrix job), are they aggregated into a single PR coverage total, or treated independently? If aggregation already works that way, documenting it would cover much of this need on its own.

Drafted by Claude (Anthropic AI assistant).