docs: document dir-index-html

assets/README.md

@@ -1,6 +1,13 @@
 # Assets loaded in with IPFS
 
-## Generating docs
+This directory contains the go-ipfs assets:
+
+* Getting started documentation (`init-doc`).
+* Directory listing HTML template (`dir-index-html` git submodule).
+
+These assets are compiled into `bindata.go` with `go generate`.
+
+## Re-generating
 
 Do not edit the .go files directly.
 
@@ -10,3 +17,34 @@ assets directory:
 ```
 go generate .
 ```
+
+## Updating dir-index-html
+
+Upstream: https://github.com/ipfs/dir-index-html
+
+dir-index-html is a git submodule. To update, run the following commands from
+this directory.
+
+```bash
+> git -C dir-index-html pull
+> git -C dir-index-html checkout vX.Y.Z # target version
+```
+
+Then, you'll need to commit the updated submodule _before_ regenerating
+`bindata.go`. Otherwise, `go generate` will checkout the checked-in version of
+dir-index-html.
+
+```bash
+> git add dir-index-html
+> git commit -m 'chore: update dir-index-html to vX.Y.Z'
+```
+
+Finally, re-generate the directory index HTML template and amend the previous
+commit.
+
+```bash
+> go generate .
+> git add bindata.go
+> git commit --amend --no-edit
+
+```