Unpredictable output

Version of Marp Tool

v1.7.2

Operating System

Windows

Environment

• OS version: ArchLinux and Alpine 3.16
• Node.js version: marp core v2.4.2, nodejs v16.18.0

How to reproduce

By default, I expect the output file to go into the current/working directory and not in the input directory (at the same level as the input file). I understand that this is debatable and suggestive.

$ marp --theme-set themes  --input-dir docs                                                                                                                                                                                                                                                                                   
[  INFO ] Converting 1 markdown...                                                                                                                                                                                   
[  INFO ] docs/slides.md => docs/slides.html 

So if I want to be sure to control the output path I'll use the --output option which has this exact purpose.

$ marp --theme-set themes --output index.html --input-dir docs
[  INFO ] Converting 1 markdown...
[  INFO ] docs/slides.md => index.html/slides.html

The --output should be relative to the current/working directory so I expect the file index.html to go to $PWD/index.html. At list an expected bad behavior would be it still output to $PWD/docs/index.html. But here what the help message says:

$   -o, --output                       Output file path (or directory when                                                                                                                                             
                                     input-dir is passed)               [string]

So when input-dir is provided, --output is interpreted as a directory and not a file anymore, so it outputs to index.html/slides.html. Meaning I can control the output dir but not longer the file name.

$ marp --theme-set themes --output test --input-dir docs
[  INFO ] Converting 1 markdown...
[  INFO ] docs/slides.md => test/slides.html

$ marp --theme-set themes --output test/index.html --input-dir docs
[  INFO ] Converting 1 markdown...
[  INFO ] docs/slides.md => test/index.html/slides.html

Same context as in https://github.com/marp-team/marp/discussions/382

Expected behavior

eg curl has 2 options:

$ curl --help all | grep '\--output'
 -o, --output <file>      Write to file instead of stdout
     --output-dir <dir>   Directory to save files in

There should definitely be an --output-file and an --output-dir option with predictable behavior and not one --output option with unpredictable behavior that change relatively to other option being used.

Actual behavior

See How to reproduce

Additional information

No response

Start by reproducing the documented commands using --input-dir and --output, then inspect the CLI's option parsing and output-path handling. Compare the current help text and behavior with the requested separate output-file and output-dir semantics. Done means the options have predictable, documented behavior for both single-file and input-directory conversions, with tests covering the examples.