How to git reset --hard a subdirectory?

Question

UPDATE: This will work more intuitively as of Git 1.8.3, see my own answer.

Imagine the following use case: I want to get rid of all changes in a specific subdirectory of my Git working tree, leaving all other subdirectories intact.

• I can do git checkout . , but git checkout . adds directories excluded by sparse checkout

• There is git reset --hard, but it won't let me do it for a subdirectory:

  > git reset --hard .
  fatal: Cannot do hard reset with paths.
  

  Again: Why git can't do hard/soft resets by path?

• I can reverse-patch the current state using git diff subdir | patch -p1 -R, but this is a rather weird way of doing this.

What is the proper Git command for this operation?

The script below illustrates the problem. Insert the proper command below the How to make files comment -- the current command will restore the file a/c/ac which is supposed to be excluded by the sparse checkout. Note that I do not want to explicitly restore a/a and a/b, I only "know" a and want to restore everything below. EDIT: And I also don't "know" b, or which other directories reside on the same level as a.

#!/bin/sh

rm -rf repo; git init repo; cd repo
for f in a b; do
  for g in a b c; do
    mkdir -p $f/$g
    touch $f/$g/$f$g
    git add $f/$g
    git commit -m "added $f/$g"
  done
done
git config core.sparsecheckout true
echo a/a > .git/info/sparse-checkout
echo a/b >> .git/info/sparse-checkout
echo b/a >> .git/info/sparse-checkout
git read-tree -m -u HEAD
echo "After read-tree:"
find * -type f

rm a/a/aa
rm a/b/ab
echo >> b/a/ba
echo "After modifying:"
find * -type f
git status

# How to make files a/* reappear without changing b and without recreating a/c?
git checkout -- a

echo "After checkout:"
git status
find * -type f

Answer 1

Note (as commented by Dan Fabulich) that:

• git checkout -- <path> doesn't do a hard reset: it replaces the working tree contents with the staged contents.
• git checkout HEAD -- <path> does a hard reset for a path, replacing both the index and the working tree with the version from the HEAD commit.

As answered by Ajedi32, both checkout forms don't remove files which were deleted in the target revision.
If you have extra files in the working tree which don't exist in HEAD, a git checkout HEAD -- <path> won't remove them.

Note: With git checkout --overlay HEAD -- <path> (Git 2.22, Q1 2019), files that appear in the index and working tree, but not in <tree-ish> are removed, to make them match <tree-ish> exactly.

But that checkout can respect a git update-index --skip-worktree (for those directories you want to ignore), as mentioned in "Why do excluded files keep reappearing in my git sparse checkout?".

Answer 2

According to Git developer Duy Nguyen who kindly implemented the feature and a compatibility switch, the following works as expected as of Git 1.8.3:

git checkout -- a

(where a is the directory you want to hard-reset). The original behavior can be accessed via

git checkout --ignore-skip-worktree-bits -- a

Answer 3

Try changing

git checkout -- a

to

git checkout -- `git ls-files -m -- a`

Since version 1.7.0, Git's ls-files honors the skip-worktree flag.

Running your test script (with some minor tweaks changing git commit... to git commit -q and git status to git status --short) outputs:

Initialized empty Git repository in /home/user/repo/.git/
After read-tree:
a/a/aa
a/b/ab
b/a/ba
After modifying:
b/a/ba
 D a/a/aa
 D a/b/ab
 M b/a/ba
After checkout:
 M b/a/ba
a/a/aa
a/c/ac
a/b/ab
b/a/ba

Running your test script with the proposed checkout change outputs:

Initialized empty Git repository in /home/user/repo/.git/
After read-tree:
a/a/aa
a/b/ab
b/a/ba
After modifying:
b/a/ba
 D a/a/aa
 D a/b/ab
 M b/a/ba
After checkout:
 M b/a/ba
a/a/aa
a/b/ab
b/a/ba

Answer 4

For the case of simply discarding changes, the git checkout -- path/ or git checkout HEAD -- path/ commands suggested by other answers work great. However, when you wish to reset a directory to a revision other than HEAD, that solution has a significant problem: it doesn't remove files which were deleted in the target revision.

So instead, I have begun using the following command:

git diff --cached commit -- subdir | git apply -R --index

This works by finding the diff between the target commit and the index, then applying that diff in reverse to the working directory and index. Basically, this means that it makes the contents of the index match the contents of the revision you specified. The fact that git diff takes a path argument allows you to limit this effect to a specific file or directory.

Since this command fairly long and I plan on using it frequently, I have set up an alias for it which I named reset-checkout:

git config --global alias.reset-checkout '!f() { git diff --cached "$@" | git apply -R --index; }; f'

You can use it like this:

git reset-checkout 451a9a4 -- path/to/directory

Or just:

git reset-checkout 451a9a4

Answer 5

A reset will normally change everything, but you can use git stash to pick what you want to keep. As you mentioned, stash doesn't accept a path directly, but it can still be used to keep a specific path with the --keep-index flag. In your example, you would stash the b directory, then reset everything else.

# How to make files a/* reappear without changing b and without recreating a/c?
git add b               #add the directory you want to keep
git stash --keep-index  #stash anything that isn't added
git reset               #unstage the b directory
git stash drop          #clean up the stash (optional)

This gets you to a point where the last part of your script will output this:

After checkout:
# On branch master
# Changes not staged for commit:
#
#   modified:   b/a/ba
#
no changes added to commit (use "git add" and/or "git commit -a")
a/a/aa
a/b/ab
b/a/ba

I believe this was the target result (b remains modified, a/* files are back, a/c is not recreated).

This approach has the added benefit of being very flexible; you can get as fine-grained as you want adding specific files, but not other ones, in a directory.

Answer 6

I'm going to offer a terrible option here, since I have no idea how to do anything with git except add commit and push, here's how I "reverted" a subdirectory:

I started a new repository on my local pc, reverted the whole thing to the commit I wanted to copy code from and then copied those files over to my working directory, add commit push et voila. Don't hate the player, hate Mr Torvalds for being smarter than us all.

Answer 7

If the size of the subdirectory is not particularly huge, AND you wish to stay away from the CLI, here's a quick solution to manually reset the sub-directory:

1. Switch to master branch and copy the sub-directory to be reset.
2. Now switch back to your feature branch and replace the sub-directory with the copy you just created in step 1.
3. Commit the changes.

Cheers. You just manually reset a sub-directory in your feature branch to be same as that of master branch !!

Answer 8

Ajedi32's answer is what I was looking for but for some commits I ran into this error:

error: cannot apply binary patch to 'path/to/directory' without full index line

May be because some files of the directory are binary files. Adding '--binary' option to the git diff command fixed it:

git diff --binary --cached commit -- path/to/directory | git apply -R --index