Replace zsh-history-substring-search with fzf

Replace the zsh-history-substring-search plugin with fzf by adding a
function that starts the fzf-history-widget when pressing <Up> with a
nonempty BUFFER. The widget then uses the buffer automatically as query
for fzf.

.config/zsh/plugins/keys.zsh

@@ -26,14 +26,6 @@ zle -N zle-line-finish
 
 bindkey '^[h' run-help
 
-## History
-## Alternatives to check out: {up,down}-line-or-search
-bindkey '^[[A'  history-substring-search-up
-bindkey "$terminfo[kcuu1]" history-substring-search-up
-bindkey '^[[B'  history-substring-search-down
-bindkey "$terminfo[kcud1]" history-substring-search-down
-bindkey '^R'    history-incremental-search-backward
-
 ## Navigation
 bindkey '^[[Z' reverse-menu-complete         # shift-tab
 bindkey '^K' kill-whole-line                 # ctrl-K
@@ -83,11 +75,39 @@ function ls-on-enter {
 	else
 		zle accept-line
 	fi
+	# See fzf-hist below
+	FZF_HIST_WENT_UP=
 }
 zle -N ls-on-enter
 bindkey "^M" ls-on-enter
 ZSH_AUTOSUGGEST_CLEAR_WIDGETS+=(ls-on-enter)
 
+# "Scroll" through history if buffer was empty but use it as query for fzf over
+# command line history if not (similar to substring-search but with fzf)
+function fzf-hist-up {
+	if [ -z "$BUFFER" ] || [ "$FZF_HIST_WENT_UP" -eq 1 ]; then
+		zle up-line-or-history
+		FZF_HIST_WENT_UP=1
+	else
+		# Will take BUFFER as query
+		fzf-history-widget
+	fi
+}
+function fzf-hist-down {
+	zle down-line-or-history
+	[ -n "$BUFFER" ] || FZF_HIST_WENT_UP=
+}
+zle -N fzf-hist-up
+zle -N fzf-hist-down
+
+## History
+# Up
+bindkey '^[[A' fzf-hist-up
+bindkey "$terminfo[kcuu1]" fzf-hist-up
+# Down
+bindkey '^[[B' fzf-hist-down
+bindkey "$terminfo[kcud1]" fzf-hist-down
+
 # Fuzzy finder bindings:
 # ^T fzf-file-widget
 # \ec (Alt-C) fzf-cd-widget

.gitmodules

@@ -40,9 +40,6 @@
 [submodule ".config/zsh/plugins/zsh-autosuggestions"]
 	path = .config/zsh/plugins/zsh-autosuggestions
 	url = https://github.com/zsh-users/zsh-autosuggestions
-[submodule ".config/zsh/plugins/zsh-history-substring-search"]
-	path = .config/zsh/plugins/zsh-history-substring-search
-	url = https://github.com/zsh-users/zsh-history-substring-search
 [submodule ".config/zsh/plugins/zsh-syntax-highlighting"]
 	path = .config/zsh/plugins/zsh-syntax-highlighting
 	url = https://github.com/zsh-users/zsh-syntax-highlighting.git