This script creates a git group and user account under Mac OS X for gitosis

create_git_user_osx.sh

#!/bin/bash

# This script creates a git group and user account under Mac OS X
# Assumes git was installed via macports (i.e. /opt/local)

USERNAME="git"
GROUPNAME="$USERNAME"
REALNAME="git version control"
PASSWORD="*"

if [[ $UID -ne 0 ]]; then echo "Please run $0 as root." && exit 1; fi

# make sure the user name is unique
unset -v new_user
new_user="$(dscl . -search /Users name "$USERNAME")"
if [[ -z "$new_user" ]]; then
  new_user="$USERNAME"               
else
  echo "User name already exists: $USERNAME"
  exit 1
fi 

# make sure the user's primary group name is unique
unset -v new_group
new_group="$(dscl . -search /Groups name "$GROUPNAME")"
if [[ -z "$new_group" ]]; then
  new_group="$GROUPNAME"             
else
  echo "Group name already exists: $GROUPNAME"
  exit 1
fi 

# make sure there is no (file or) home directory of the same name already
if [[ -e "/Users/$USERNAME" ]]; then
  echo "\nUser $USERNAME already exists at /Users/$USERNAME"
  exit 1
fi

# get unique id numbers (uid, gid) that are greater than 500
unset -v i new_uid new_gid idvar
declare -i new_uid=0 new_gid=0 i=500 idvar=0

while [[ $idvar -eq 0 ]]; do 
   i=$[i+1]
   if [[ -z "$(dscl . -search /Users uid $i)" ]] && [[ -z "$(dscl . -search /Groups gid $i)" ]]; then
      new_uid=$i
      new_gid=$i
      idvar=1
      #break
   fi
done

if [[ $new_uid -eq 0 ]] || [[ $new_gid -eq 0 ]]; then echo 'Getting unique id numbers (uid, gid) failed!'; exit 1; fi

# Create the group
echo "creating group $new_gid: $GROUPNAME"
dscl . -create /Groups/$GROUPNAME
dscl . -append /Groups/$GROUPNAME gid "$new_gid"

# Create the user account
echo "creating user $new_uid: $USERNAME ($REALNAME)"
dscl . -create /Users/$USERNAME
dscl . -append /Users/$USERNAME UserShell /bin/bash
dscl . -append /Users/$USERNAME RealName "$REALNAME"
dscl . -append /Users/$USERNAME UniqueID "$new_uid"
dscl . -append /Users/$USERNAME PrimaryGroupID "$new_gid"
dscl . -append /Users/$USERNAME NFSHomeDirectory /Users/$USERNAME
dscl . -passwd /Users/$USERNAME "$PASSWORD"

# Create the home directory
createhomedir -c

# Create .bashrc
cat > /Users/$USERNAME/.bashrc << EOF

if [ -x /usr/libexec/path_helper ]; then
    eval `/usr/libexec/path_helper -s`
fi

export PATH="/opt/local/bin:/opt/local/sbin:$PATH"
export PATH=$(git --exec-path):$PATH

EOF

# Grant the user ssh access
echo "granting $USERNAME ssh access"
dscl . -append /Groups/com.apple.access_ssh GroupMembership $USERNAME

# Add _www to git group so web server can access git user's content
dscl . -append /Groups/git GroupMembership _www

echo "User: $USERNAME and Group: $GROUPNAME created."