Remove the Python 2.4 dependency and use just 'python'

Many Linux distributions are including python2.5 by default, as
it is the latest stable release of the language.  Using python2.4
(and asking users to specifically install it) is just cruel and
unusual punishment.

Signed-off-by: Shawn O. Pearce <sop@google.com>

main.py

@@ -15,7 +15,7 @@
 # limitations under the License.
 
 magic='--calling-python-from-/bin/sh--'
-"""exec" python2.4 -E "$0" "$@" """#$magic"
+"""exec" python -E "$0" "$@" """#$magic"
 if __name__ == '__main__':
   import sys
   if sys.argv[-1] == '#%s' % magic:

project.py

@@ -517,6 +517,9 @@ class Project(object):
         old_merge = self.bare_git.rev_parse('%s@{1}' % merge)
       except GitError:
         old_merge = merge
+      if old_merge == '0000000000000000000000000000000000000000' \
+         or old_merge == '':
+        old_merge = merge
     else:
       # The upstream switched on us.  Time to cross our fingers
       # and pray that the old upstream also wasn't in the habit

repo

@@ -20,7 +20,7 @@ REPO_REV='stable'
 # limitations under the License.
 
 magic='--calling-python-from-/bin/sh--'
-"""exec" python2.4 -E "$0" "$@" """#$magic"
+"""exec" python -E "$0" "$@" """#$magic"
 if __name__ == '__main__':
   import sys
   if sys.argv[-1] == '#%s' % magic:
@@ -28,7 +28,7 @@ if __name__ == '__main__':
 del magic
 
 # increment this whenever we make important changes to this script
-VERSION = (1, 4)
+VERSION = (1, 5)
 
 # increment this if the MAINTAINER_KEYS block is modified
 KEYRING_VERSION = (1,0)