This pull request primarily focuses on enhancing the functionality of the command-line interface (CLI) in the internal/cli/cli.go file. The changes enable the CLI to handle multiple files instead of a single file. This is achieved by modifying the CLI struct and several functions within it, including Run, validateInput, replaceProcess, and filterProcess. The cli_test.go file has also been updated to test the new functionality, and a new test file testdata/testa.txt has been added.

Changes to CLI struct and functions:

• internal/cli/cli.go: Updated the CLI struct to replace the filePath string field with a filePaths slice of strings, allowing multiple files to be processed.
• internal/cli/cli.go: Modified the Run function to iterate over the filePaths slice and process each file. Additional code was added to handle the case when no file paths are provided. [1] [2] [3]
• internal/cli/cli.go: The validateInput function was updated to validate each file path in the filePaths slice.
• internal/cli/cli.go: The replaceProcess and filterProcess functions were modified to accept an io.Reader parameter, which is used to read from the file being processed.

Test updates:

• internal/cli/cli_test.go: Added new test cases in TestRun_successProcess to test the processing of multiple files.
• internal/cli/cli_test.go: Added a new test function TestRun_failToProvideFiles to test scenarios where file provision fails.
• internal/cli/cli_test.go: Updated existing test functions to pass an io.Reader parameter when calling ReplaceProcess and FilterProcess. [1] [2]

Additional changes:

• internal/cli/export_test.go: Updated the exported ReplaceProcess and FilterProcess functions to accept an io.Reader parameter.
• internal/cli/testdata/testa.txt: Added a new test file for testing the processing of multiple files.