Do not unbind C-b if a user still uses it

Fixes #5

CHANGELOG.md

@@ -6,6 +6,8 @@
 - do not make any decision about the prefix, just enhance it
 - update `README.md`. List options set in the plugin.
 - do *not* set `mode-mouse on` by default because some users don't like it
+- if a user changes default prefix but binds `C-b` to something else, do not
+  unbind `C-b`
 
 ### v1.0.0, 2014-07-30
 - initial work on the plugin

sensible.tmux

@@ -41,6 +41,17 @@ key_binding_not_set() {
 	fi
 }
 
+key_binding_not_changed() {
+	local key="$1"
+	local default_value="$2"
+	if $(tmux list-keys | grep -q "bind-key[[:space:]]\+${key}[[:space:]]\+${default_value}"); then
+		# key still has the default binding
+		return 0
+	else
+		return 1
+	fi
+}
+
 main() {
 	# OPTIONS
 
@@ -97,7 +108,9 @@ main() {
 	# if C-b is not prefix
 	if [ $prefix != "C-b" ]; then
 		# unbind obsolte default binding
+		if key_binding_not_changed "C-b" "send-prefix"; then
 			tmux unbind-key C-b
+		fi
 
 		# pressing `prefix + prefix` sends <prefix> to the shell
 		tmux bind-key "$prefix" send-prefix