[RFC PATCH 0/1] Extended tree format for mixed submodules and conflicts

Today at the Contributor Summit we discussed two different proposals
that might benefit from some extensions to trees: submodules of a
different hash algorithm and first-class conflicts.

Peff suggested that we could do something hideous to the tree format to
allow for extensions to submodules of different algorithms.  In the
interests of prototyping things to see how much people like or hate the
idea, I've written up an example spec and included a script below so we
can see how current Git implementations handle this.  (This was part of
my lunchtime activity.)

Git itself handles this data as a submodule, which seems to be the least
bad option for a new mode type.  `git fsck` complains about the mode, as
expected.

I don't intend to actually implement this proposal or do anything
serious with it, but I offer it as a discussion piece about what we
could do if we wanted in a minimally incompatible way.  If you really
hate it, that's okay; I agree it's a little gross.

----
#!/bin/sh -e

# This script requires a printf that supports hex escapes because I'm too lazy
# to convert things into octal.

rm -fr test-repo
git init --object-format=sha1 -b dev test-repo
cd test-repo
tree_oid=$(/usr/bin/printf '130000 \x91\x82\x80s256\x01\xdf\xac\xbf\xee\xdf\xac\xbf\xee\xdf\xac\xbf\xeesubmodule\x00\xde\xad\xbe\xef\xde\xad\xbe\xef\xde\xad\xbe\xef\xde\xad\xbe\xef\xde\xad\xbe\xef' | git hash-object -t tree -w --literally --stdin)
commit_oid=$(git commit-tree -m + "$tree_oid")
git reset --hard "$commit_oid"
git show HEAD
----

brian m. carlson (1):
  Define an extended tree format

 Documentation/Makefile                     |  1 +
 Documentation/gitformat-extended-tree.adoc | 77 ++++++++++++++++++++++
 Documentation/meson.build                  |  1 +
 3 files changed, 79 insertions(+)
 create mode 100644 Documentation/gitformat-extended-tree.adoc