[pitivi] pitivi-git-environment: Respect the user's __git_ps1 if present

[Jean-FranÃois Fortin Tam <jfft src gnome org>]

commit 5c8778b0b4a3979d9e25c54d20f6cbeacee1237d
Author: Jean-FranÃois Fortin Tam <nekohayo gmail com>
Date:   Sat Sep 8 15:10:26 2012 -0400

    pitivi-git-environment: Respect the user's __git_ps1 if present

 bin/pitivi-git-environment.sh |   17 ++++++++++++++++-
 1 files changed, 16 insertions(+), 1 deletions(-)
---
diff --git a/bin/pitivi-git-environment.sh b/bin/pitivi-git-environment.sh
index beac32e..4a475d9 100755
--- a/bin/pitivi-git-environment.sh
+++ b/bin/pitivi-git-environment.sh
@@ -300,6 +300,21 @@ fi
 if [ $ready_to_run == 1 ]; then
     cd $PITIVI/pitivi
     # Change the looks of the prompt, to help us remember we're in a subshell.
-    changed_PS1='PS1="\[$(tput bold)$(tput setb 1)$(tput setaf 7)\]PiTiVi env:\w $ \[$(tput sgr0)\]"'
+    # If the user has some custom git bash helpers, try preserving them.
+
+    function function_exists {
+        FUNCTION_NAME=$1
+        [ -z "$FUNCTION_NAME" ] && return 1
+        declare -F "$FUNCTION_NAME" > /dev/null 2>&1
+        return $?
+        }
+    if function_exists __git_ps1
+    then
+        # Display "PTV env:", path, the output of __git_ps1, " $ "
+        changed_PS1='PS1="\[$(tput bold)$(tput setb 1)$(tput setaf 7)\]PTV env:\w\[$(tput sgr0)\]\$(__git_ps1)$ "'
+    else
+        # Display "PTV env:", path, " $ "
+        changed_PS1='PS1="\[$(tput bold)$(tput setb 1)$(tput setaf 7)\]PTV env:\w\[$(tput sgr0)\] $ "'
+    fi
     bash --rcfile <(cat ~/.bashrc; echo $changed_PS1)
 fi