Better handle edge-cases in $PROMPT_COMMAND (#128)

Some libraries do things like `PROMPT_COMMAND="$PROMPT_COMMAND ; _new_addition"`, that's a space-semicolon-space. It would be counter-productive to try to account for all possibilities, so just swap the install string for a no-op.

Clean up no-op, it it's all that's left

Co-authored-by: Ryan Caloras <[email protected]>

Author: gaelicWizard

bash-preexec.sh

@@ -326,14 +326,16 @@ __bp_install() {
     local existing_prompt_command
     # Remove setting our trap install string and sanitize the existing prompt command string
     existing_prompt_command="${PROMPT_COMMAND:-}"
-    existing_prompt_command="${existing_prompt_command//${__bp_install_string}[;$'\n']}" # Edge case of appending to PROMPT_COMMAND
-    existing_prompt_command="${existing_prompt_command//$__bp_install_string}"
+    # Edge case of appending to PROMPT_COMMAND
+    existing_prompt_command="${existing_prompt_command//$__bp_install_string/:}" # no-op
+    existing_prompt_command="${existing_prompt_command//$'\n':$'\n'/$'\n'}" # remove known-token only
+    existing_prompt_command="${existing_prompt_command//$'\n':;/$'\n'}" # remove known-token only
     __bp_sanitize_string existing_prompt_command "$existing_prompt_command"
 
     # Install our hooks in PROMPT_COMMAND to allow our trap to know when we've
     # actually entered something.
     PROMPT_COMMAND=$'__bp_precmd_invoke_cmd\n'
-    if [[ -n "$existing_prompt_command" ]]; then
+    if [[ "${existing_prompt_command:-:}" != ":" ]]; then
         PROMPT_COMMAND+=${existing_prompt_command}$'\n'
     fi;
     PROMPT_COMMAND+='__bp_interactive_mode'