ensure root $HOME expands to /

https://mywiki.wooledge.org/BashPitfalls?rev=565#line-1-81
LucasLarson/dotfiles@98cf52dcec

Signed-off-by: Lucas Larson <LucasLarson@riseup.net>

readme.adoc

@@ -100,7 +100,7 @@ using Fig^], or you can just clone this repository, run the following
 command, and then restart your terminal:
 [source,zsh]
 $ printf '%s\n' '. /path/to/gunstage.plugin.zsh' \
-  >>"${HOME-}"'/.'"${SHELL##*[-./]}"'rc'
+  >>"${HOME%/}"'/.'"${SHELL##*[-./]}"'rc'
 
 Requirements
 ~~~~~~~~~~~~