gitk: command not found

Question

Environment: Mac OSX 10.10. When I was trying to use gitk, it shows:

Coda-2:~ Coda$ gitk
-bash: gitk: command not found

I think the reason is the old version of git. Here is some information, and I have already typed brew update.

Coda-2:~ Coda$ git --version
git version 1.9.3 (Apple Git-50)
Coda-2:~ Coda$ brew install git 
Warning: git-2.4.0 already installed, it's just not linked

What is this message: it's just not linked?

Furthermore, I check the path of git:

Coda-2:~ Coda$ which git
/usr/bin/git

It should be in /usr/bin/local/git? How to fix it?

UPDATE

I figure it out, thank @TimCastelijns.

brew doctor said:

Warning: You have unlinked kegs in your Cellar
Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
those kegs to fail to run properly once built. Run `brew link` on these:

    git

So, I typed:

Coda-2:~ Coda$ brew link git
Linking /usr/local/Cellar/git/2.4.0... 220 symlinks created

Then I typed gitk, and it worked and the path changed to /usr/local/bin/git. However, when I want to check the version of git. It still showed the old version, why?

Coda-2:~ Coda$ git --version
git version 1.9.3 (Apple Git-50)

Answer 1

First, check git version.

Type git --version, and it may show old version.

Next, update your Homebrew

Type brew update.

Then, download the latest version. brew install git

Note that, if it show Warning: git-2.4.0 already installed, it's just not linked

We can check brew doctor, in my case, it told me to use brew link git

Finally, type brew install git again and restart terminal.

I can use gitk and upgrade git version to the latest version.

Update

Since gitx is no longer supported for OSX 10.12, I recommend using Gitx-dev