simplest way to get the SHA of an arbitrary git object?

I want a git command that simply outputs the SHA of an arbitrary object (commit, tree, blob, whatever). Basically:

$ git sha HEAD
7b78f727c91edc7726f3c31113bc7b1509fea163
$ git sha master^:CHANGELOG
0dcc5f003ed89c30a8d0376a29d546c20449fd90

...and so forth. This should be the simplest thing in the world, but I can't figure out a good way of doing it. I don't mind using an alias to a complex, option-laden git command, but it seems like I must just be missing a really simple dereference command that git must surely use under开发者_如何学Go the hood all the time.

For the purposes you have given, your git sha is actually git rev-parse.

% git rev-parse HEAD
47753f420d6ec7d84f8705e9acb67693745b4a8b
% git rev-parse origin/pu^:Documentation/RelNotes-1.7.1.txt
9d89fedb36b4d6fa7c8a6a8487cc47b4ca542e3a