Updating submodules

Move a driver to a newer commit, check it and open the pull request that pins it.

1. Merge the change in the driver's repository first. The umbrella only ever points at commits on a driver's main.

2. Bump the pointer here.

   git switch -c bump/hf-tmc9660-driver
   git submodule update --init external/hf-tmc9660-driver
   git -C external/hf-tmc9660-driver fetch origin main
   git -C external/hf-tmc9660-driver checkout origin/main
   git add external/hf-tmc9660-driver
   git commit -m "Bump hf-tmc9660-driver for <the change>"
   

3. Build it where it is used. Point hf-core's hf-core-drivers submodule at your branch and run its host build and the ESP32 examples of the boards that enable the driver.

4. Open the pull request here, naming the driver change it brings in. After the merge, bump hf-core-drivers in hf-core.

Adding a driver

1. git submodule add https://github.com/hardfoc/<repo>.git external/<repo>.
2. Add an entry for it to tools/docs/drivers.yml: group, chip, vendor, function, bus, language and whether it has a documentation site. Check each fact against the driver's README.
3. Run hardfoc-docs gen and mkdocs build --strict; the catalogue gains a card.

Checking where every submodule points

git submodule status            # commit of each submodule; a leading '-' means not initialised
git submodule foreach --quiet 'echo "$name $(git describe --tags --always)"'

Next: Coding standards.