Make CVS value expansion work in git.

[mithro]

A lot of the files in repository have the old $Header: XXX $ and $Id: XXX $ style tags.

This pull request removes the expanded tags in the code and uses git filters + attributes to expand them on checkout.

For this to work, a person needs to run git config --local include.path ../.gitconfig to enable this to work so make setup-git is added to the Makefile.

• $Id$ and $Revision$ gets expanded to the git describe --always --long output
• $Date$ gets expanded to the date of the last value commit value.
• $Author$ gets expanded to the email address of the person who last committed to the file.
• $Header$ gets expanded to <filename> <git describe> <last modification commit date> <last modification author address>.

[RTimothyEdwards]

Pulled, but I have not followed the instructions above. When you say "a person needs to run", do you mean me? "../.gitconfig" implies that there is a ".gitconfig" outside of the repo? Why?

[mithro]

@RTimothyEdwards A person needs to run make setup-git after checking out for the first time.

The git config --local include.path ../.gitconfig means --local means relative to local git config file (which is .git/config). So <basepath>/.git/../.gitconfig which is the .gitconfig file at <basepath>/.gitconfig inside the repo.