docs/development: add spec bump instructions

docs/development.md

@@ -1,5 +1,41 @@
-## Developing FCCT
+# Developing FCCT
 
-### Creating a release:
+## Creating a release
 
 Create a [release checklist](https://github.com/coreos/fcct/issues/new?template=release-checklist.md) and follow those steps.
+
+## Bumping spec versions
+
+Up to this point in FCCT development, FCC versions and `base` versions have been 1:1 mapped onto Ignition specs, and we have not had any distro-specific sugar. This checklist therefore describes bumping the Ignition spec version, `base` version, and `config` version, while leaving the distro sugar version unchanged. If your scenario is different, modify to taste.
+
+### Stabilize Ignition spec version
+
+- Bump `go.mod` for new Ignition release and update vendor.
+- Update imports. Drop `-experimental` from Ignition spec versions in `base/vB_exp/translate_test.go`.
+
+### Bump base version
+
+- Rename `base/vB_exp` to `base/vB` and update `package` statements. Update imports.
+- Copy `base/vB` to `base/vB+1_exp`.
+- Update `package` statements in `base/vB+1_exp`.
+
+### Bump config version
+
+- Rename `config/vC_exp` to `config/vC` and update `package` statements. Update imports.
+- Drop `-experimental` from `registry` in `config/config.go`.
+- Drop `-experimental` from examples in `docs/`.
+- Copy `config/vC` to `config/vC+1_exp`.
+- Update `package` statements in `config/vC+1_exp`. Bump its base dependency to `base/vB+1_exp`.
+- Import `config/vC+1_exp` in `config/config.go` and add `fcos+C+1-experimental` to `registry`.
+
+### Bump Ignition spec version
+
+- Add translation function for experimental spec `I+1` to `distro/fcos/vF`. Revendor Ignition.
+- Bump Ignition types imports and rename `ToIgnI` and `TestToIgnI` functions in `base/vB+1_exp`. Bump Ignition spec versions in `base/vB+1_exp/translate_test.go`.
+- Bump Ignition types imports in `config/vC+1_exp`. Update `Translate` to call `ToIgnI+1` functions. Update versions in `TranslateBytes` comment.
+
+### Update docs
+
+- Copy the `C-exp` spec doc to `C+1-exp`. Update the header and the version numbers in the description of the `version` field.
+- Rename the `C-exp` spec doc to `C`. Update the header, delete the experimental config warning, and update the version numbers in the description of the `version` field.
+- Update `docs/migrating-configs.md` for the new spec version. Copy the relevant section from Ignition's `doc/migrating-configs.md`, convert the configs to FCCs, convert field names to snake case, and update wording as needed. Add subsections for any new FCC-specific features.