Fail on error tags

Failing on error is useful for scripts which use && abstraction
to exectue targets. They are included in all derived targets and
also in git's main macro
Add reset macro

Simulates the git reset [options] [commit/index] semantic
Add archive command

Archive let's you create a quick dirty zip for any git tree. Pl. be
informed that some of the switches ( like --output ) are supported
only in git>=1.7 as I have tested. Atlease they break with git-1.5.
Hence handle with care ;)
Add git-clean

git-clean helps remove untracked project generated files. Documentation
at http://www.kernel.org/pub/software/scm/git/docs/git-clean.html
Merge pull request #1 from snktagarwal/master

Merge latest changes from snktagarwal