Re: Checkout to different directory at certain commit without changing index

[Phillip Wood <phillip.wood123@gmail.com>]

Hi Ondra

On 13/05/2024 08:26, Ondra Medek wrote:
> Hello,
> I need a simple script for unskilled users to do a fast checkout (LFS
> friendly) of the current local Git clone at a certain commit to a
> different directory I.e. something like "copy at a point in history".

I think using

     git archive "$commit" --format=tar |
        { cd "$output_directory" && tar -xf -; }

is probably the simplest solution. If you don't want to rely on tar then 
something like

     GIT_DIR="$(git rev-parse --path-format=absolute --git-dir)" &&
     GIT_COMMON_DIR="$(git rev-parse --path-format=absolute 
--git-common-dir)" || exit
     GIT_INDEX_FILE="$GIT_DIR/tmp-index-$$"
     export GIT_DIR GIT_COMMON_DIR GIT_INDEX_FILE
     unset GIT_WORK_TREE
     mkdir "$output_directory" && cd "$output_directory" &&
     git read-tree -u "$commit"
     status=$?
     rm "$GIT_INDEX_FILE"
     exit $status

Which uses a temporary index file should work (note I haven't tested 
it). You may want to add "--recurse-submodules" and/or 
"--no-sparse-checkout" to the "git read-tree" commandline.

Best Wishes

Phillip

> IMO all possible solutions are summarized in this thread
> https://stackoverflow.com/questions/160608/do-a-git-export-like-svn-export
> I describe some of them with my remarks:
> 
> - git checkout-index : works with HEAD only.
> - git archive: influenced by export-ignore and export-subst
> attributes, so may not produce exact copy of sources. (And needs tar).
> - git worktree add -d : needs cleanup: git prune or git remove.
> - git clone: Unfortunately, -b param cannot work with commit hash and
> does not respect local worktree settings (e.g. autocrlf). So, a
> solution may be a bit complicated: git clone -s -n . dest/path ; cp
> .git/config dest/path/.git ; cd dest/path ; git co -q <commit-ish> ;
> rm -rf .git
> - git checkout: Unfortunately, modifies Git index, so some action to
> revert index is necessary after: git --work-tree=/path/to/checkout/
> checkout -f -q <tree-ish> -- ./
> 
> For me, the best solution is with git clone, because it does not
> modify Git index nor any source working tree settings, so no cleanup
> is necessary. But it's a bit complicated, though. It seems to me that
> "git checkout" could do this better and simpler if it would have some
> param to not modify the Git index. Is it possible to enhance git
> checkout? Or is there any other simple solution not mentioned in the
> SO thread?
> 
> Thank you
> Ondra Medek
>