How do you copy a specific git commit to the staging area?

git

Solution

The `git checkout` command writes through the index/staging-area to the work directory, so checking out files does the job (though it updates the work directory whether you want that or not).

The problem, of course, is that `git checkout commit` switches branches, or detaches HEAD. The trick to avoid this is to check out specific files, which avoids this branch-switching:

git checkout branch-one -- path/to/file.ext

If you check out the entire tree, you'll get all the files. Assuming you're in the top level directory:

git checkout branch-one -- .

will do the trick.

One other caveat: this will not remove from the staging area any file that does not exist in `branch-one`. If you want that as well, start by removing everything (the staging area will get repopulated by checking out all the files in the other branch):

git rm -rf .
git checkout branch-one -- .

(adjust as needed if you don't want to copy the other branch's .gitignore, etc; note that you can restore specific files from `branch-two`, aka `HEAD`, with:

git checkout HEAD -- path

if desired).

(As usual, be sure the state of the work directory is clean before doing this.)

Problem

Original source