The installer from the git homepage installs into /usr/local/git by default. See also this answer. However, if you install XCode4, it will install a git version in /usr/bin. To ensure you can easily upgrade from the website and use the latest git version, edit either your profile information to place /usr/local/git/bin before /usr/bin in the $PATH or edit /etc/paths and insert /usr/local/git/bin as the first entry (see this answer).
Is it in your PATH? If so just run which git in the terminal and it will tell you.
you can simply use this command on a terminal to find out git on unix platforms (mac/linux) -
whereis git
This command should return something like - /usr/bin/git or any other location where git is installed
If you have fresh installation / update of Xcode, it is possible that your git binary can't be executed (I had mine under /usr/bin/git). To fix this problem just run the Xcode and "Accept" license conditions and try again, it should work.
On Linux the command is whereis. Alternatively you can issue find / -name git and wait for an eternity. Alternatively try echo $PATH | sed "s/:/ /g" | xargs -L 1 ls | grep git
Mostly in /usr/local/git (there are also /etc/paths.d/git and /etc/manpaths.d/git items).
Usually some of the applications have been known to take it from the Xcode.app path also: /Applications/Xcode.app/Contents/Developer/usr/bin/
Coda 2, prefers this path than the soft link at /usr/bin.
simply type in which git in your terminal window and it will show you exactly where it was installed.
On most of UNIX based sys, its at /usr/bin/git (if installed with default options)
all git related scripts are at /usr/libexec/git-core
On Mojave
The binary is in
/usr/bin/git
The related scripts are here
/Applications/Xcode.app/Contents/Developer/usr/libexec/git-core/git
You can also try with /usr/local/bin/git it worked for me
Source: Stackoverflow.com