To delete multiple Git branches at once, you can use the combination of git branch, grep, and xargs commands. The git branch command lists all local branches, grep -v master filters out the master branch from the output, and xargs git branch -D deletes each branch that matches the pattern.

Here's an example:

git branch | grep -v master | xargs git branch -D

This command will list all the Git branches, exclude the master branch, and then pass the remaining branch names to git branch -D to delete them.

To make it more convenient, you can create an alias in your ~/.bashrc or equivalent file:

alias delete_branches="git branch | grep -v master | xargs git branch -D"

After adding the alias, you can simply use the delete_branches command to delete multiple branches at once.

Please note that deleting branches is a potentially destructive operation, so use it with caution and double-check before executing the command.