From: phillip.wood123@gmail.com
Date: Tue, 14 May 2024 10:01:36 GMT
Subject: Re: Checkout to different directory at certain commit without changing index
Message-ID: <45674580-e7f6-48aa-ac17-3e0b96acace9@gmail.com>
In-Reply-To: <CAJsoDaFhTcm0fEw3+Ba4PvTjPYxscALeLN2kBgs4YYz8Bg-R7g@mail.gmail.com>

Hi Ondra

On 13/05/2024 18:23, Ondra Medek wrote:
> Hi Phillip,
> 
> besides dependency on tar, I do not want to use git-archive because
> it's influenced by export-ignore and export-subst attributes, too (as
> I have mentioned).
> 
> Thanks for git read-tree, seems it's exactly what I need. Just git
> read-tree has complained that -u switch needs -m or --reset switches.
> And I have simplified it to

Sorry I'd forgotten about that

> git --work-tree="$destdir" read-tree --index-output="$destdir".git -u
> --reset "$commit"

You should be aware that --reset will happily overwrite files in the 
destination directory, using -m instead would stop existing files being 
overwritten. If you change to -m you must set GIT_INDEX_FILE instead of 
using --index-output otherwise only the files that differ from the 
current index will be checked out. Also using a relative path for the 
index file specified with --index-output or GIT_INDEX_FILE is error 
prone when running the command from a subdirectory of the repository. I 
avoided suggesting --work-tree because I wasn't sure how it handled 
relative paths when run from a subdirectory but I think it is in fact ok.

> rm -f "$destdir"/.git
> 
> May I post this solution to the SO thread I have mentioned?

That's entirely up to you but I'd make sure it works with relative paths 
and note the difference between --reset and -m.

Best Wishes

Phillip

> Thanks very much
> 
> Ondra
> 
> On Mon, 13 May 2024 at 17:28, Phillip Wood <phillip.wood123@gmail.com> wrote:
>>
>> 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
>>>