--input-file does not accept '-' for stdin; breaks Unix convention

[MattDevy]

Summary

--input-file - is rejected with file not found: - instead of being read from stdin. The - filename convention for stdin is broadly expected across Unix tools (curl --data-binary @-, kubectl apply -f -, jq, cat, etc.), and works around the lack of body-field flags on commands like cloud serverless projects search create (filed separately as #328).

--input-file is on most mutating commands and all the helpers (es bulk, es search, es helpers bulk-ingest, es helpers scroll-search, kb saved-objects post-saved-objects-import, cloud serverless projects search create, ...), so this affects a wide surface.

Reproducer

$ elastic version
{"version": "0.1.1"}

$ echo '{"name":"x","region_id":"aws-us-east-1"}' \
    | elastic cloud serverless projects search create --input-file - --dry-run
Error: --input-file: file not found: -

Usage: elastic cloud serverless projects search create [options]
...

Process substitution works as a current workaround:

$ elastic cloud serverless projects search create \
    --input-file <(echo '{"name":"x","region_id":"aws-us-east-1"}') --dry-run
dry run: inputs valid, no action performed

But that's bash/zsh-specific and unfamiliar to many users; the - convention is what most reach for first.

Expected behavior

When --input-file - is supplied, read the body from stdin until EOF. This matches the convention used by curl, kubectl, jq, pass, and most other Unix tools that take --input-file / -f / --data.

Applying the change once in the shared input-file resolver should make every command that accepts --input-file benefit, without per-command work.

Environment

• elastic v0.1.1 on macOS