cleanup & do not clear fzf query between ctrl+{f,g}

[laur89]

• minor bash cleanup, such as:
  • variable localization
  • use bash syntax (eg [[]] vs [])
  • improve param quoting
  • capitalize global parameters
• preserve user input query in fzf between ctrl+f & ctrl+g options by utilizing --print-query fzf option;
• instead of recursively calling capture(), run the command in a loop in capture();