git: pass `id` attribute of `pygit2.Tree` object
`pygit2`'s Repository object expects an instance of `Oid`
to return the corresponding object, instead of the object
itself.
After this change and D9062, `hg commit -i` seems to work,
unless it hits a case folding assertion (ie trying to add
a file like `README.md`).
Differential Revision: https://phab.mercurial-scm.org/D9068
# Files that just need to be migrated to the formatter.
# Do not add new files here!
mercurial/cext/manifest.c
mercurial/cext/osutil.c
# Vendored code that we should never format:
syntax: glob
contrib/python-zstandard/**.c
contrib/python-zstandard/**.h
hgext/fsmonitor/pywatchman/**.c
mercurial/thirdparty/**.c
mercurial/thirdparty/**.h