When I run this command: cordova plugin add https://git-wip-us.apache.org/repos/asf/cordova-plugin-camera.git I got an error. It says: Fetching plugin "https://git-wip-us.apache.org/repos/asf/cordova-plugin-camera.git" via git clone
Error: "git" command line tool is not installed: make sure it is accessible on your PATH.

To solve this problem
Firstly: Go to http://git-scm.com/download/win and download and install the relevant file.

git download install

git download install

git installation settings configuration

git installation settings

Secondly, system environment variable must be set.
So go to start menu -> right click on “Computer” and “Properties” ->
on the left side “Advanced System Setting” -> “Advanced” tab -> “Environment Variables…” -> “System variables” -> “Path” variable -> “Edit”
Add “;C:\Program Files (x86)\Git\bin” to end of the “Variable value”.

set system variable

set system variable

Alternative way to install git : open a command prompt and command below:
npm install -g git -verbose
note: -g means globally, in other saying it loads from internet. -verbose means list output of command.

run the “cordova plugin add https://git-wip-us.apache.org/repos/asf/cordova-plugin-camera.git”  again in command prompt . If it still gets an error, then run  a command prompt as Administrator. Then run the same command.