coredesktop/skills/sibling-project-format.md

# Skill: Formatting a Repository as a CoreDesktop Sibling Project

## Overview

A sibling project is a git repository that builds on CoreDesktop. Users install
one with CoreDesktop's `sibling` command, and from then on CoreDesktop's
`update` command keeps it up to date.

Follow this document when you are working in a sibling repository and need it
to install and update correctly under CoreDesktop. A repository needs no
special files to be installable. It becomes useful by adding two optional
scripts at its top level:

| File         | When it runs                                                 |
|--------------|--------------------------------------------------------------|
| `install.sh` | Once, when the user runs `sibling add`, and again if they re-run it |
| `update.sh`  | On every `update`, right after the repo has been pulled      |

If you want full control over how the project updates, see
`sibling-project-updates.md` (custom `updates.d` hooks) instead. Use one
approach or the other, not both, or the project updates twice.

## What CoreDesktop Does

### `sibling add <url>` (or `sibling`, which asks for the URL)

1. Works out the project name from the last part of the URL, dropping `.git`:
   `git@gitea.federated.computer:david/my-tools.git` → `my-tools`.
2. Clones the repo into `~/.local/share/siblings/<name>`, or, if that folder
   already holds a clone of the same URL, runs `git pull --ff-only` there.
3. If `install.sh` exists, runs `bash install.sh` with the repo folder as the
   working directory. Its input and output are the user's terminal.
4. Reports success only if every step above succeeded.

### `update`

CoreDesktop runs its own update hooks in order (`10-pacman.sh` … `70-claude.sh`).
Next, `updates.d/71-siblings.sh` takes each sibling in alphabetical order and:

1. Runs `git pull --ff-only --quiet` in its folder.
2. If the pull succeeded and `update.sh` exists, runs `bash update.sh` with the
   repo folder as the working directory.

A failed pull or a non-zero exit from `update.sh` is printed and listed in
`update`'s "Done, with errors in: …" summary. Other siblings still update.
CoreDesktop's end-of-run hooks (GNOME settings, firmware, cleanup, reboot
check) run after all siblings.

### `sibling remove <name>`

This only deletes `~/.local/share/siblings/<name>`. CoreDesktop has no uninstall
step for siblings, so anything `install.sh` set up elsewhere stays.

## Rules for the Repository

### Layout

- Put `install.sh` and `update.sh` at the top level of the repo. Other names or
  locations are ignored.
- Both scripts are run with `bash`, so they don't need to be executable, but a
  `#!/bin/bash` line keeps them runnable by hand.
- Locate files relative to the script, not to a hard-coded path. The user may
  also clone the repo somewhere else and run `install.sh` by hand.
  ```bash
  SELF="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
  ```

### Environment

- The scripts run as separate `bash` processes, so they inherit **no**
  variables or functions from CoreDesktop. In particular `$COREDESKTOP` is
  **not** set. Use the path directly:
  ```bash
  COREDESKTOP="$HOME/.local/share/coredesktop"
  ```
- CoreDesktop's helpers are available by sourcing `utils.sh`:

  | Function                 | What it does                                        |
  |--------------------------|-----------------------------------------------------|
  | `install_packages ...`   | Installs pacman/AUR packages via `yay`, skipping installed ones |
  | `remove_packages ...`    | Removes installed pacman/AUR packages               |
  | `remove_flatpaks ...`    | Uninstalls flatpaks that are installed              |
  | `enable_services ...`    | Enables systemd services not yet enabled            |
  | `install_script src dst` | Copies a file atomically and makes it executable    |
  | `is_installed pkg`       | True if a pacman package is installed               |

- `sudo` prompts for a password as normal. CoreDesktop does not grant
  passwordless sudo to siblings.

### `install.sh`

- **Exit non-zero on failure.** `set -e` near the top is the simplest way.
  `sibling` then tells the user it failed and how to retry.
- **Make it safe to re-run.** Re-running `sibling add` is how users repair an
  install, so skip work that is already done instead of failing on it.
- It may prompt the user, since it runs in their terminal.
- Install commands into `~/.local/bin` (already on `PATH` under CoreDesktop)
  with `install_script`.

### `update.sh`

- **Make it idempotent.** It runs on every `update`, usually with nothing to do.
- **Don't prompt.** Users expect `update` to run through without questions,
  apart from `sudo` passwords.
- **Exit non-zero only for real failures**, so that `update`'s error summary
  stays meaningful.
- **Print what it's doing.** CoreDesktop prints only the project's name before
  it runs.
- The repo has already been pulled, so `update.sh` always runs its newest
  version. Use it to apply changes made since the last update: new packages,
  updated commands in `~/.local/bin`, config migrations.
- It's fine to omit `update.sh` if pulling the repo is enough, for example when
  `~/.local/bin` holds symlinks into the repo.

### Keep pulls working

`update` pulls with `--ff-only` and never merges or resets. A pull fails if:

- **History on the default branch is rewritten** (force-pushed). Never do this.
- **Tracked files are edited in place** in the clone and a new commit touches
  them. Scripts must not write into tracked files. Write generated files,
  caches and per-machine state outside the repo (e.g. `~/.config/<name>/`), or
  into paths listed in `.gitignore`.

### Authentication

`sibling` clones with plain `git`. A private repo works only if the user can
already clone it (SSH key, credential helper, or a password typed at the
prompt). Every later `update` needs the same access.

## Templates

Share the install logic between the two scripts so that packages or commands
added later reach existing machines through `update`, not just new installs.

`install.sh`:

```bash
#!/bin/bash
#
# Purpose : Install <project> (run by CoreDesktop's `sibling add`)

set -e

SELF="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
COREDESKTOP="$HOME/.local/share/coredesktop"
source "$COREDESKTOP/utils.sh"

# One-time setup: prompts, accounts, initial config...
mkdir -p "$HOME/.config/<project>"

# Everything that update.sh also needs to keep current
bash "$SELF/update.sh"

echo "<project> installed."
```

`update.sh`:

```bash
#!/bin/bash
#
# Purpose : Keep <project> current (run by CoreDesktop's `update`)

set -e

SELF="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
COREDESKTOP="$HOME/.local/share/coredesktop"
source "$COREDESKTOP/utils.sh"

PACKAGES=(
  jq
  ripgrep
)
install_packages "${PACKAGES[@]}"

mkdir -p "$HOME/.local/bin"
install_script "$SELF/bin/<project>" "$HOME/.local/bin/<project>"
```

## Testing

Test in a throwaway home folder so nothing touches the real one. Point
`sibling` at a local clone; it accepts any URL or path that `git clone` does.

```bash
export HOME="$(mktemp -d)"
mkdir -p "$HOME/.local/share"
ln -s /path/to/real/coredesktop "$HOME/.local/share/coredesktop"

# Install
bash "$HOME/.local/share/coredesktop/sibling" add /path/to/sibling-repo

# Commit a change in /path/to/sibling-repo, then run the update hook the way
# `update` does
( source "$HOME/.local/share/coredesktop/updates.d/71-siblings.sh"; is_installed && run_update )

# Re-run the install to check it is safe to repeat
bash "$HOME/.local/share/coredesktop/sibling" add /path/to/sibling-repo
```

Scripts that call `sudo`, `yay` or `systemctl` still change the real system
even with a temporary `HOME`. Test those on a machine or VM you don't mind
changing.

## Checklist

- [ ] The repo can be cloned by URL by the people who will install it
- [ ] `install.sh` (optional) is at the top level, exits non-zero on failure,
      and is safe to re-run
- [ ] `update.sh` (optional) is at the top level, idempotent, doesn't prompt,
      and prints what it's doing
- [ ] Scripts find their own files relative to the script and set
      `COREDESKTOP="$HOME/.local/share/coredesktop"` themselves
- [ ] Nothing writes to tracked files in the clone, and the default branch is
      never force-pushed
- [ ] The project doesn't also copy a hook into CoreDesktop's `updates.d/`
- [ ] The README tells users to install with
      `sibling add <url>`