A reminder to use single quotes when writing commit messages

Originally published at https://rivea0.github.io/blog.

Using backticks in the shell results in command expansion, for example:

echo `which cp`

is the same as

echo $(which cp)

It finds the directory the cp command is in (executes the which command), and then prints it to the screen.

Normally, when using double quotes, many types of expansions do not work (like word-splitting and brace expansions), but with command expansion, this is not the case.

Commands inside backticks are executed if they are inside double quotes.

When writing a message to git commit, rendering the name of a function in monospace, for example, is easy to do using backticks.

So, my hypothesis is that when I do something like

git commit -m "Add `doThis` function"

If doThis is a command, it will be executed.

So, if we write something like

git commit -m "Add `which cp` thing"

It will replace it with the directory that cp is in, so that our commit message will look like:

Add /bin/cp thing

In fact, after trying it, it turns out to be true, and this Stack Overflow answer has a nice short explanation.

Single quotes, on the other hand, suppress all expansions, so if written like this:

git commit -m 'Add `which cp` thing'

It won't execute which cp, but write it as it is:

Add `which cp` thing

So, I think it is safer to use single quotes, whether you want to use a code block a la markdown styling or not.

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This enlightenment is thanks to the "Seeing the World as the Shell Sees It" chapter from William E. Shotts' book The Linux Command Line: A Complete Introduction.