How to check out history safely?

In most cases checking out a previous commit is safe. But since .gitignore is version controlled as well, checking out an old commit with an older version of .gitignore can have serious side effects.

Imagine that our latest commit includes the following files:

.gitignore ignores config.properties
config.properties our main configuration file

Since git ignores config.properties reverting to an older commit will keep config.properties as is. But since older commit doesn't ignore config.properties it now appears as an added file.

In order to checkout the latest commit again, one can either:

commit file
ignore file
remove files
or stash files.

Each of which isn't ideal. Each comes with a side effect.

Committing files or ignoring files (updating .gitignore) creates a new head. Removing files, or stashing them will remove those files our of version control. Meaning that when returning to our latest commit those files will be missing.

What is the safest approach to checkout a previous commit?

Solution

If you are worried about any changes to your working directory, just use git worktree

git worktree add ../<new dir> <sha or branch>

Edit: sorry misremembered the syntax best to check the docs