Split prompt into two lines

Prior to this change, we were setting PS1 manually and having to muck
with the \[, \] pairs for terminal escapes was proving to be too much.
Instead, we moved to using a function used in PROMPT_COMMAND which
displays the user, hostname and directory on one line, followed by the
actual prompt line which displays the git status.

bash/bashrc.d/git_prompt.bash

@@ -3,6 +3,7 @@
 # Define the colors used by the prompt
 if [[ ! -z $TERM && "$TERM" != "dumb" ]]
 then
+    T_R=$(tput setaf 1) # Red
     T_B=$(tput setaf 4) # Blue
     T_G=$(tput setaf 2) # Green
     T_Y=$(tput setaf 3) # Yellow
@@ -10,17 +11,51 @@ then
 else
     # We've probably been invoked by an SSH command, there's no terminal
     # to deal with. Don't bother coloring the prompt.
+    T_R=''
     T_B=''
     T_G=''
     T_Y=''
     T_S=''
 fi
 
+# Define a default prompt string
+export PS1='\$ '
+
+# Define a default __git_ps1 in case we don't have git prompt functionality
+__git_ps1()
+{
+    :
+}
+
 # Import the Git prompt shell functions. These can be found
 # @github:git/git/contrib/completion/git_prompt.sh
 if [ -f $HOME/.git_prompt.sh ]; then
     source $HOME/.git_prompt.sh
-    export PS1='\[$T_B\]\u@\h \[$T_S\][\[$T_G\]$(smartwd)$(__git_ps1 " \[$T_Y\](%s)")\[$T_S\]]\$ '
-else
-    export PS1='\[$T_B\]\u@\h \[$T_S\][\[$T_G\]$(smartwd)\[$T_S\]]\$ '
+fi
+
+# Prompt header function, prints user, hostname and current directory
+prompt_header()
+{
+    local last_result="$?"
+
+    echo
+    echo -ne "${T_Y}$(date '+%F %T')${T_S} "
+    echo -ne "${T_B}${USER}@${HOSTNAME} ${T_S}[${T_G}$(smartwd)${T_S}]"
+    if [[ $last_result != 0 ]]
+    then
+        echo -ne " ${T_R}!! ${last_result} !!${T_S} "
+    fi
+    echo
+
+    # Configuration for __git_ps1
+    GIT_PS1_SHOWCOLORHINTS=yes
+    GIT_PS1_SHOWDIRTYSTATE=yes
+    GIT_PS1_SHOWUNTRACKEDFILES=yes
+    GIT_PS1_SHOWUPSTREAM=verbose
+    __git_ps1 '' '\$ ' '(%s)'
+}
+
+if [[ ! -z $TERM && "$TERM" != "dumb" ]]
+then
+    export PROMPT_COMMAND='prompt_header'
 fi