Append git's branch name to command prompt
The trick to get the quoting right is to have eveything double-quoted, except for $(__git_ps1 "(%s)"), which is single-quoted.
source ~/.git-completion.bashfunction prompt{local WHITE="\[\033[1;37m\]"local GREEN="\[\033[0;32m\]"local CYAN="\[\033[0;36m\]"local GRAY="\[\033[0;37m\]"local BLUE="\[\033[0;34m\]"export PS1="${GREEN}\u${CYAN}@${BLUE}\h ${CYAN}\w"' $(__git_ps1 "(%s)") '"${GRAY}"}promptAn alternative solution is to replace $( with \$( in the code in the question.
Background information: Two substitutions take place: first at export PS1="..." time, and later when the prompt is displayed. You want to execute __git_ps1 each time the prompt is displayed, so you have to make sure that the first substitution keeps $(...) intact. So you write either '$(...)' or "\$(...)". These are the two basic ideas behind the solutions I've proposed.