Git alias with parameters

In the company I work we use the gitflow workflow and in every feature branch we make sure that part of its name is the task’s id which includes a unique number. So what we end up with is something like:

feature/T12345-make-the-app-rock

What I wanted was an easy way to checkout a branch using just the number. I wanted (spoiler: and succeeded) something like this:

git ch 12345

Terminal

Lets see how we can checkout a branch without an alias but by using the task’s number.

Get the branch

We can get the branch by listing all branches (git branch) and then grep for the one that contains the task’s number:

git branch | grep 12345

this will return feature/T12345-make-the-app-rock

Checkout to it

Having a way to get the branch makes the checkout quite easy since we can use bash’s command substitution to execute the above commands and use the result directly in the checkout:

git checkout $(git branch | grep 12345)

Put it in a function

We are now able to checkout the task’s branch but it would be nice if we could change the task’s number more easily. Lets create a function and pass the number as a parameter:

• The $1 is where the parameter will be used (if we had more parameters we would use $2 for the second, $3 for the third etc).
• You can check the function by writing it directly in the terminal. Just make sure that you add newlines (press enter):

The alias

We can change branches easily but once we close the current terminal session we lose everything. Our goal is to have all that in a git alias.

Creating an alias can be achieved either by using git config

git config –global alias.ch checkout

or by doing it manually and adding the alias directly into the .gitconfig file (usually located in the home directory). The file should end up with something like:

Having just the alias will not help us much. As is, it will work only if we give it the entire branch:

git ch feature/T12345-make-the-app-rock

What we need is a way to connect the function that we created with the alias.

The answer is provided by git itself since it has a way to create aliases that do not execute a git command but an external command:

However, maybe you want to run an external command, rather than a Git subcommand. In that case, you start the command with a ! character. This is useful if you write your own tools that work with a Git repository.

git docs

Following the docs we can change the gitconfig file to look like this (this time the change must be made only manually because our function will need to have newlines):

What will happen when we write git ch 12345 is:

1. git ch will be replaced with everything inside the "..." (minus the !) ending up with two commands
2. the first one creates the f function and
3. the second one calls f with the parameter 12345: f 12345

And that’s it! We now have a git alias that will allow us to checkout a branch using part of its name.

feature image by Zach Reiner @ unsplash