CLI: Add "--json" as an additional output format to show commands #5220

As an operator, developer, or CI automation user, I want consistent machine‑readable JSON output for all photoprism show … CLI commands so I can script checks, integrate with tooling, and validate configurations without parsing human‑formatted tables.

Implemented Changes

• JSON format support across all “show” commands
  • Flag: --json, -j (part of shared report.CliFlags).
  • Renderer: pkg/txt/report supports Format(JSON) and renders tables as JSON.
• JSON shape and keys
  • Single-table commands (file-formats, thumb-sizes, video-sizes, sources, search-filters) return a top-level array of row objects.
  • Keys derive from column names using snake_case (spaces/dashes → “_”, lowercase, punctuation removed).
  • Multi-section and special cases:
    • show config → { "sections": [{ "title", "items": [ {...} ] }, ...] } (unchanged).
    • show config-options → top-level array (flattened across sections).
    • show config-yaml → top-level array (flattened across sections).
    • show metadata → { "items": [ {...} ], "docs": [ {...} ] } (docs omitted when --short).
  • All values are strings (parity with CSV/TSV for stable tooling).
• Flag conflict validation
  • Exactly one of --json | --md | --csv | --tsv; conflicts return cli.Exit with code 2.
• Markdown output preserved for docs
  • show config-options --md and show config-yaml --md render section headings + tables for docs ingestion.
• Help text and descriptions
  • report.CliFlags usage strings clarified (“print machine‑readable …”).
  • Command descriptions for show config-options and show config-yaml note that text/Markdown is sectioned while JSON/CSV/TSV are flat lists.
• Plus/Pro builds
  • Commands that use report.CliFlags inherit --json automatically; config-options/config-yaml JSON is flat there as well.

Note: JSON output for the photoprism show config-options and photoprism show config-yaml commands is a flat, top-level array, unlike the standard and Markdown-formatted outputs.

How To Use

• Examples
  • photoprism show sources --json | jq '.[0]'
  • photoprism show thumb-sizes --json | jq '.[0] | {name, width, height}'
  • photoprism show file-formats --json | jq 'map({format, type, extensions}) | .[0]'
  • photoprism show config --json | jq '.sections[0].items[0]' # still sectioned
  • photoprism show config-options --json | jq '.[0]' # now flat array
  • photoprism show config-yaml --json | jq '.[0]' # now flat array
  • photoprism show metadata --json | jq '{items: (.items|length), docs: (.docs//[])|length}'
  • photoprism show metadata --json --short | jq 'keys' # docs omitted
• Flag conflict check
  • photoprism show sources --json --csv; echo $? # expect exit code 2

Manual Test Checklist

• Single-table commands emit a JSON array of objects
  • Keys are snake_case, values are strings; sample keys match column intent (source, priority, description, …).
• Multi-section and special cases
  • show config → sections[].title present; sections[].items is an array of objects.
  • show config-options → top-level array (no sections).
  • show config-yaml → top-level array (no sections).
  • show metadata → items present; docs present unless --short is set.
• Markdown for docs remains sectioned
  • photoprism show config-options --md includes “### Authentication” and a valid Markdown table.
  • photoprism show config-yaml --md includes per-section headings and tables.
• CSV/TSV behave unchanged (single table, delimited).
• Plus/Pro (if available locally) accept --json and produce valid JSON; config-options/config-yaml are flat arrays there, too.

Acceptance Criteria

• --json output is available and valid JSON for all photoprism show … commands.
• Keys are canonicalized snake_case; values are strings.
• Conflicting format flags return cli.Exit with code 2.
• Markdown for config-options/config-yaml remains sectioned for docs ingestion.
• No regressions in CSV/TSV/default output.
• Plus/Pro CLIs using report.CliFlags accept --json and render valid JSON; config-options/config-yaml are flat.

Notes

• Code: pkg/txt/report/* (JSON renderer, key canonicalization); internal/commands/show_*.go (CliFormatStrict; JSON assembly where needed).
• CLI help updated to clarify sectioned text/Markdown vs flat machine formats.
• Docs/specs updated (as of 2025-09-21) to reflect JSON shapes and Markdown docs integration.