Add @override_copy_command to force copy command.

Fixes #90

README.md

@@ -171,6 +171,31 @@ Configuration
     -   <kbd>Y</kbd> (shift-y) — "put" selection. Equivalent to copying a
         selection, and pasting it to the command line.
 
+
+### Default and Preferred Clipboard Programs
+
+tmux-yank does its best to detect a reasonable choice for a clipboard
+program on your OS.
+
+If tmux-yank can't detect a known clipboard program then it uses the
+`@custom_copy_command` tmux option as your clipboard program if set.
+
+If you need to always override tmux-yank's choice for a clipboard program,
+then you can set `@override_copy_command` to force tmux-yank to use whatever
+you want.
+
+Note that both programs _must_ accept `STDIN` for the text to be copied.
+
+An example of setting `@override_copy_command`:
+
+``` tmux
+# ~/.tmux.conf
+
+set -g @custom_copy_command 'my-clipboard-copy --some-arg'
+# or
+set -g @override_copy_command 'my-clipboard-copy --some-arg'
+```
+
 ### Linux Clipboards
 
 Linux has several cut-and-paste clipboards: `primary`, `secondary`, and

scripts/helpers.sh

@@ -27,6 +27,9 @@
 custom_copy_command_default=""
 custom_copy_command_option="@custom_copy_command"
 
+override_copy_command_default=""
+override_copy_command_option="@override_copy_command"
+
 # helper functions
 get_tmux_option() {
     local option="$1"
@@ -75,6 +78,10 @@
 custom_copy_command() {
     get_tmux_option "$custom_copy_command_option" "$custom_copy_command_default"
 }
+
+override_copy_command() {
+    get_tmux_option "$override_copy_command_option" "$override_copy_command_default"
+}
 # Ensures a message is displayed for 5 seconds in tmux prompt.
 # Does not override the 'display-time' tmux option.
 display_message() {
@@ -108,7 +115,9 @@
 
 clipboard_copy_command() {
     # installing reattach-to-user-namespace is recommended on OS X
-    if command_exists "pbcopy"; then
+    if [ -n "$(override_copy_command)" ]; then
+        override_copy_command
+    elif command_exists "pbcopy"; then
         if command_exists "reattach-to-user-namespace"; then
             echo "reattach-to-user-namespace pbcopy"
         else