git - Get the hash of the current HEAD of a repo using only HTTP -

i know if have git repo checked out, can use git cli current commit hash. there way on http, without cloning repo?

for example, let's want current hash of https://github.com/jashkenas/coffeescript. manually, can go page, press y on keyboard, , see hash (at time of writing) 1f197fcc1bf1a15bc45a6b23fb3f706ffcb77025. means if @ later point wanted download coffeescript source @ moment, download https://github.com/jashkenas/coffeescript/archive/1f197fcc1bf1a15bc45a6b23fb3f706ffcb77025.zip , give me source.

is there way using http (e.g. curl)? can hit endpoint tell me current hash of default branch? generalizing bit, there endpoints tell me hash of

• the head of default branch,
• the head of given branch, or
• a particular tag?

if wanted information on github specifically, retrieve using the github api, return large json structure exhaustive information on state of branch:

https://api.github.com/repos/jashkenas/coffeescript/branches/master 

(or remove branch name more terse listing of branches , heads.)

for git repositories hosted on other web services, it's possible fetch resource /info/refs under repository (e.g, http://example.com/repo.git/info/refs) listing of branches, e.g.:

2aae6c35c94fcfb415dbe95f408b9ce91ee846ed    refs/heads/master 

however, this not available on github, because github disabled "dumb" http transport in 2011 performance reasons. replacement "smart" transport, while far superior git's own use, isn't usable outside context.