datatree import (clean)

[flamingbear]

This is the exact same steps followed in #8656

But hopefully with a clean history.

I am copying the notes from the previous PR below.

https://github.com/flamingbear/rewritten-datatree is the version of datatree that was m
erged in this PR.

---

Previous PR notes
This PR imports xarray-contrib/datatree and its history to pydata/xarray/xarray/datatree_

Step one of issue #8572.
This imports the datatree code without exposing DataTree as a public API.

git filter repo https://github.com/newren/git-filter-repo was used to preserve some history for the merge.

Datatree tags were renamed to legacy-datatree-{tag}:

git filter-repo --tag-rename '':'legacy-datatree-'

Links to xarray-contrib/datatree original PRs are preserved by rewriting the messages using a replace-message file.

# standard github style pull request (#39)
regex:\(#(\d+)\)==>https://github.com/xarray-contrib/datatree/pull/\1

# "Merge pull request #11 from TomNicholas/single_datanode_class"
regex:pull request #(\d+)==>https://github.com/xarray-contrib/datatree/pull/\1

Links to the xarray-contrib/datatree Issues are preserved with a replace-text file.

# standard comment change "  # see issue #38"
regex:(\s*?#.*[ ])#(\d+)==>\1https://github.com/xarray-contrib/datatree/issues/\2

# also "    @pytest.mark.xfail(reason="Indexing needs to return whole tree (GH #77)")"
regex:(\(GH #(\d+)\))==>(GH https://github.com/xarray-contrib/datatree/issues/\2)

The datatree repo was relocated to a subdirectory

git-filter-repo --to-subdirectory xarray/datatree_

and the prepared datatree repository was added as a remote and merged into xarray.

git merge prepared-datatree/main --no-commit --allow-unrelated-histories

This should allow work to begin on the rest of the steps in #8572

[keewis]

One tiny comment that I have is to put the PR numbers ((#8656, #8688)) at the end of the commit message, but I think I can do that just before doing the merge itself.

@pydata/xarray, can we temporarily freeze main until this is done? This shouldn't take more than an hour after the meeting.

[welcome]

Congratulations on completing your first pull request! Welcome to Xarray! We are proud of you, and hope to see you again!

[dcherian]

Woot! Thanks everyone!

[mathause]

This makes git bisect very confusing - suddenly you get an empty folder (just a comment - nothing to do here)