question: why do I get "remote: fatal: Not a git repository: '.'" ?

post-receive hookscript
=======================
  cd $PROJECTDIR
  # update to latest source
  pwd
  ls -la
  git pull
  git reset --hard
  git checkout staging




1. post-receive hook executed on commandline (WORKS)
====================================================
/var/www/staging/subsystem/pulse
ls -la
total 40
drwxr-xr-x 4 leon  mannetje 4096 2013-02-27 12:21 .
drwxr-xr-x 3 billy mannetje 4096 2013-02-26 16:56 ..
drwxr-xr-x 8 leon  mannetje 4096 2013-02-27 12:20 .git
-rw-rw-r-- 1 leon  mannetje  120 2013-02-27 12:10 .gitignore
drwxr-xr-x 8 leon  mannetje 4096 2013-02-27 12:21 src
remote: Counting objects: 7, done.
remote: Compressing objects: 100% (4/4), done.
remote: Total 4 (delta 3), reused 0 (delta 0)
Unpacking objects: 100% (4/4), done.
From /work/projects/pulse
   b5f34ee..c5d5807  staging    -> origin/staging
Updating b5f34ee..c5d5807
Fast-forward
 src/.htaccess.example |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
HEAD is now at c5d5807 git deploy test


2. post-receive hook executed when I run 'git push' (ERROR)
===========================================================

:!git push
error: refs/heads/issue443 does not point to a valid object!
Counting objects: 7, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (4/4), 359 bytes, done.
Total 4 (delta 3), reused 0 (delta 0)
remote: /var/www/staging./subsystem/pulse
remote: ls -la
remote: total 40
remote: drwxr-xr-x 4 leon  mannetje 4096 2013-02-27 12:20 .
remote: drwxr-xr-x 3 billy mannetje 4096 2013-02-26 16:56 ..
remote: drwxr-xr-x 8 leon  mannetje 4096 2013-02-27 12:20 .git
remote: -rw-rw-r-- 1 leon  mannetje  120 2013-02-27 12:10 .gitignore
remote: drwxr-xr-x 8 leon  mannetje 4096 2013-02-27 12:20 src
remote: fatal: Not a git repository: '.'
remote: fatal: Not a git repository: '.'
remote: fatal: Not a git repository: '.'