zsh:glog: Only pipe to fzf if stdout is a tty

This makes it easy to use `glog` in a pipe as replacement for `git log
--oneline`, for example to count the commits.

.config/zsh/autoload/git/glog

@@ -127,7 +127,12 @@ else
 	)
 fi
 
-# Display the commits in the above format and pipe that into fzf.
-git log "$formatshort" "$dateshort" --color=always "$@" \
-| env LESS="$LESS${LESS:+ }-+F" fzf "${fzf_args[@]}"
+# Display the commits in the above format and pipe that into fzf if stdout is a
+# terminal.
+if [ -t 1 ]; then
+	git log "$formatshort" "$dateshort" --color=always "$@" \
+	| env LESS="$LESS${LESS:+ }-+F" fzf "${fzf_args[@]}"
+else
+	git log "$formatshort" "$dateshort" --color=always "$@"
+fi
 return 0