CLDR-16425 v43 update cldr-json docs

UPDATING.md

@@ -9,23 +9,60 @@
 
 ## Instructions
 
-1. Check out the [`cldr-staging`](https://github.com/unicode-org/cldr-staging) repo as a sibling to cldr-json. This will be the data source.
-2. Check out the [`cldr`](https://github.com/unicode-org/cldr) repo as a sibling to cldr-json and set it up so [maven builds are possible](https://cldr.unicode.org/development/maven).
+### Setup
+
+Check out repos (If you use a different directory layout, see Customization)
+
+1. Check out this repo [`cldr-json`](https://github.com/unicode-org/cldr-json). (Note: Big.)
+2. Check out the [`cldr-staging`](https://github.com/unicode-org/cldr-staging) repo as a sibling to cldr-json. This will be the data source. (Note: Very big.) Use a release tag if possible.
+3. Check out the [`cldr`](https://github.com/unicode-org/cldr) repo as a sibling to cldr-json and set it up so [maven builds are possible](https://cldr.unicode.org/development/maven).
+
+Make sure your `cldr-json` directory is otherwise clean (`git status`)
+
+### Building
+
+1. `cd` to `cldr-json`
+2. *Delete* the `cldr-json/cldr-json` subdirectory (the subdirectory of `cldr-json`).  This way, git will tell you what has changed, and you can see if any files failed to regenerate.
 3. Run the script `cldr-generate-json.sh`
-4. Data will be updated in the `cldr-json` subdirectory.
-5. Run the script `cldr-generate-zips.sh` to generate zipfiles under `dist/`
-6. npm packages can be updated as well. Each sub-subdirectory of `cldr-json/cldr-json` is a separate npm package. The following script will preview
-(dry run) publishing to npm under the `beta` tag.
+4. Data will be updated in the recreated `cldr-json` subdirectory.
+
+#### Troubleshooting
+
+- `git status` is your friend. At least, until too many files change.
+- If a `cldr-json/supplemental` or `cldr-json/other` or other such subdirectory shows up not prefixed with `cldr-`, there's probably something wrong with the `cldr-json` mapping.
+  - Sadly, there is no documentation about how to update the tooling. TODO: [CLDR-16445](https://unicode-org.atlassian.net/browse/CLDR-16445)
+
+### Publishing
+
+1. Run the script `cldr-generate-zips.sh` to generate zipfiles under `dist/` - these are suitable for uploading to a release page
+2. create a release tag such as `43.0.0` in this repository. or `43.0.0-ALPHA2`.  Create a GitHub release, use other [releases](https://github.com/unicode-org/cldr-json/releases) as a guide.
+3. npm packages can be updated as well. Each sub-subdirectory of `cldr-json/cldr-json` is a separate npm package. The following script will preview
+(dry run) publishing to npm under the `beta` tag. Check the version carefully!
 
 ```shell
 (cd cldr-json; for repo in $(ls); do (cd $repo; npm publish --tag beta --dry-run); done)
 ```
 
+### Customization
+
 See `cldr-config.sh` for customization options.
 
 You can create an executable script named `local-config.sh` with
 values to update, for example `VERSION`, `TYPES`, `MATCH` or `DRAFTSTATUS`
 
+Example, if you have a different directory layout:
+
+```shell
+# VERSION defaults to calculating the version
+VERSION=43.0.0-ALPHA2
+
+# CLDR_DIR defaults to ../cldr
+CLDR_DIR=../cldr-maint-43
+
+# INDATA defaults to ../cldr-staging/production
+INDATA=../cldr-staging-other/production
+```
+
 ## Licenses
 
 - Usage of CLDR data and software is governed by the [Unicode Terms of Use](http://www.unicode.org/copyright.html)