How do I enable https support in libcurl?

This worked for me:

Re-install curl and install it using the following commands (after unpacked):

$ ./configure --with-darwinssl    
$ make    
$ make test    
$ sudo make install

When you run the command "curl --version" you'll notice that the https protocol is now present under "protocols".

A helpful site if you run into curl problems: https://curl.haxx.se/docs/install.html

How can I determine the path to the curl that brew is using?

Homebrew uses /usr/bin/curl, i.e the version that ships with Mac OS X, as you can see here.

That being said, and as you precise, your problem is probably related to the version of libcurl that is linked with git and used for http:// and https://.

Perform a which git to determine which is the version you are being used (mine is installed under /usr/local).

Then scan the shared libraries used as follow:

$ otool -L /usr/local/git/libexec/git-core/git-http-push | grep curl
/usr/lib/libcurl.4.dylib

Replace /usr/local/ with the install directory that corresponds to your git.

Since the libcurl version used by your git exec lacks of HTTPS support, this will tell you what is this version and where it is installed.