How can I copy a file from another Git branch?

A scenario I've run into a few times is the need to copy a file from one branch to another. While cherry-picking might be of some use in this case, there's a more straightforward way to copy a file from one branch to another.
You might be familiar with git checkout, namely as a way to switch between branches. But it can do much more than that. By using git checkout <branch> <pathspec>, you can copy a file from another branch to the current branch.
The last portion of the command actually accepts a pathspec, allowing you to specify files or directories. This can be useful when you want to copy more than one file at a time.

# Usage: git checkout <branch> <pathspec>

git checkout patch-2
git checkout patch-1 "30seconds.txt"
# `patch-2` branch now contains the 30seconds.txt file from `patch-1`

git checkout patch-3
git checkout dev "src/*"
# `patch-3` branch now contains the contents of the src directory from `dev`

The last portion of the command actually accepts a pathspec, allowing you to specify files or directories. This can be useful when you want to copy more than one file at a time.

From 30-seconds-of-code: copy-file-from-branch