rmarkdown 2.25

• Fixed a bug that filenames beginning with - cause incorrect invocation of Pandoc (thanks, @mbaynton, #2503).

• Documented how to merge output_format_dependency() to the output format (thanks, @atusy, #2508).

• ioslides_presentation() now correctly works with new shiny 1.7.5 (thanks, @nicolasgaraycoa, #2514, @gadenbuie, #2516).

• Added a new argument metadata to the pre_knit function in output_format() so that users will have access to the YAML metadata of the input document before knitting it (#2485). Please note that if you define pre_knit for a custom output format, you are strongly recommended to leave a ... argument in pre_knit, so we (rmarkdown package authors) are free to add more arguments to pre_knit without breaking your code. If your pre_knit function does not have the ... argument, you will get a warning.