test:tldr:d755c

This command checks if the value of the environment variable "GIT_BRANCH" is an empty string or not. Here is the breakdown of the command:

• test is a command used in Unix-like operating systems to perform tests and evaluations.
• -z is a test operator used with the test command to check if a string is empty.
• "${$GIT_BRANCH}" is the variable being checked. The syntax ${VAR_NAME} is used to access the value of a variable. In this case, the variable being checked is GIT_BRANCH. However, the use of "$" before $GIT_BRANCH is incorrect syntax. It should be either "${GIT_BRANCH}" or just $GIT_BRANCH.

So, when this command is executed, it checks if the value of the GIT_BRANCH variable is an empty string. If it is empty, the command returns a true or "0" exit status. If it is not empty, the command returns a false or non-zero exit status.