cmd ref: clarify metric file type auto detection and it's relationship with `-x` (add, modify, show subcommands)

JSON metric files are detected by dvc metrics based on their file extensions (see iterative/dvc/issues/1553).

E.g. if we see that output has .json suffix, we could safely assume that it is --type json without explicitly specifying it.

[jorgeorpinel]

I saw this (iterative/dvc.org/pull/228) and thought we need to make changes in the docs of repro

Hmmm good find, yes maybe the -m option of dvc repro in https://dvc.org/doc/command-reference/repro#options could use updating as well. But again, this issue’s main goal is stated in the title, and involves the dvc metrics add/modify/show subcommands.

But I’m starting to think this whole issue may be outdated though, as it’s over a year old. For starters, we only support JSON metrics right now (soon to add YAML).

Let’s ask @shcheklein or @efiop to confirm.

Meanwhile @srishti-nema I recommend you either a) learn how to use DVC metrics and try to reproduce this issue (JSON metric type autodetection by file extension when -t isn’t provided to dvc metrics show for example) and figure out whether all the documents we’ve mentioned are up to date; or b) pick another issue. Thanks

[shcheklein]

I think it’s not relevant anymore.