vhs-tape-authoring

name	vhs-tape-authoring
description	> Use when this capability is needed.

VHS Tape Authoring

Use this skill to create or edit VHS tape files and their supporting setup scripts for gh-infra demos.

When To Use

• Adding a new demo for a gh-infra feature
• Editing an existing tape's scenario or timing
• Setting up mock data for a new demo
• Understanding how mock-gh works

Tape File Structure

Every .tape follows this pattern:

# 1. Output targets
Output demo-<name>.gif
Output demo-<name>.mp4

# 2. Theme and layout
Set Theme { ... }
Set Shell "bash"
Set FontSize 20
Set Width 1400
Set Height 900
Set Padding 20
Set WindowBar ""
Set TypingSpeed 50ms

# 3. Hidden setup
Hide
Type "source /data/setup-<name>.sh"
Enter
Sleep 2s
Type "clear"
Enter
Sleep 500ms
Show

# 4. Visible demo sequence
Sleep 700ms
Type "gh infra ..."
Enter
Sleep 3s
# ... more actions ...
Sleep 2s

Themes

Two themes are available. Copy from an existing tape:

Theme	Based on	Use in
gh-infra-dark	Tokyo Night	All tapes except light variant
gh-infra-light	Tokyo Night Day	demo-light.tape only

VHS Commands Reference

Command	Usage	Notes
Type "text"	Types text into terminal	Respects TypingSpeed
Enter	Press Enter
Escape	Press Escape
Tab	Press Tab
Sleep 1s	Wait	Use ms or s units
Hide / Show	Toggle recording visibility	Setup runs in Hide
Output <file>	Set output file	Always set both .gif and .mp4

Timing Guidelines

Action	Recommended Sleep
After source setup-*.sh	2s
After clear	500ms
Before first command	700ms-1s
After Type before Enter	350ms-500ms
After running gh infra plan/apply	5s-8s (depends on output size)
After confirmation (y + Enter)	5s-6s
End of demo	2s-3s

Setup Script Pattern

Each tape has a corresponding setup-<name>.sh:

#!/usr/bin/env bash
set -euo pipefail

# 1. Install gh-infra binary
cp /data/.gh-infra /usr/local/bin/gh-infra
chmod +x /usr/local/bin/gh-infra

# 2. Create gh wrapper (routes "gh infra" to real binary, rest to mock)
cat > /usr/local/bin/gh << 'WRAPPER'
#!/usr/bin/env bash
if [[ "$1" == "infra" ]]; then
  shift
  exec /usr/local/bin/gh-infra "$@"
fi
exec /data/mock-gh "$@"
WRAPPER
chmod +x /usr/local/bin/gh

# 3. Populate mock data
export MOCK_DIR=/tmp/mock-data
mkdir -p "$MOCK_DIR/<owner>/<repo>"
cat > "$MOCK_DIR/<owner>/<repo>/view.json" << 'JSON'
{ ... }
JSON

# 4. Create demo working directory and manifests
mkdir -p /tmp/demo
cat > /tmp/demo/<manifest>.yaml << 'YAML'
...
YAML

# 5. Set prompt
export PS1='$ '

The gh wrapper is the key mechanism:

• gh infra ... → real gh-infra binary (spinners, diffs, colors are genuine)
• gh repo view ..., gh api ... etc. → mock-gh returns prepared data

mock-gh Data Layout

mock-gh is data-driven and scenario-agnostic. It reads from $MOCK_DIR:

$MOCK_DIR/{owner}/{repo}/
  view.json                       # gh repo view --json response
  commit-settings.json            # squash/merge commit title/message (optional)
  contents/{path}                 # raw file content (base64-encoded on the fly)

Supported mock responses

gh command pattern	Data source	Default if missing
repo view --json description,...	view.json	Empty/default settings
repo view --json defaultBranchRef	hardcoded	"main"
REST /actions/permissions	hardcoded	enabled:true, allowed_actions:all
/contents/{path} (GET)	contents/{path} file	404 (new file)
secret list	hardcoded	empty
variable list	hardcoded	[]
repo edit, write APIs	no-op	success with delay

All mock responses include a random 200-500ms delay to simulate network latency.

Checklist: Adding a New Demo

1. Check resource headroom: Adding a tape increases parallel resource demand. Count existing tapes (ls docs/tapes/*.tape | wc -l) and multiply by per-container memory (--memory in vhs.sh). If the total approaches or exceeds Docker Desktop's memory allocation, warn the user to either increase Docker Desktop memory (recommended: 16 GB) or consider reducing per-container resources. See the vhs-demo skill for details.

2. Create the tape: docs/tapes/demo-<name>.tape

   • Copy theme/layout from an existing tape
   • Set Output demo-<name>.gif and Output demo-<name>.mp4
   • Script the demo sequence

3. Create the setup script: docs/tapes/setup-<name>.sh

   • Make it executable: chmod +x
   • Populate $MOCK_DIR with the GitHub state the demo needs
   • Create manifest YAML in /tmp/demo/

4. Update Makefile: Add the new GIF to the cp line in the demo target:

   @cp docs/tapes/demo-<name>.gif docs/public/ 2>/dev/null || true
   

5. Test locally: Run make demo or test the single tape:

   docker run --rm -v docs/tapes:/data -w /data gh-infra-vhs demo-<name>.tape
   

6. Verify output: Check that both .mp4 and .gif are non-zero size

Tips

• The Hide/Show block is critical. Viewers should never see the setup phase.
• Keep demos focused on one feature. Aim for under 30 seconds of visible recording.
• If mock-gh doesn't support an API your feature needs, extend mock-gh with a new pattern-match block.
• Type speed is global (TypingSpeed 50ms). For dramatic pauses, use Sleep between Type and Enter.

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Source: babarot/gh-infra — distributed by TomeVault.