[clangd-dev] [monorepo] Much improved downstream zipping tool available

[David Greene via clangd-dev]

He all,

I've updated the downstream fork zipping tool that I posted about last
November [1].  It is much improved in every way.  The most important
enhancements are:

- Does a better job of simplifying history

- Handles nested submodules

- Will put non-submodule-update content in a subdirectory of the
  monorepo

- Updates tags

In addition there are plenty of the requisite bug fixes.  The latest
version of the tool can be found here:

https://github.com/greened/llvm-git-migration/tree/zip

With the nested submodules and the subdirectory features, the tool can
now take a downstream llvm repository with submodules (e.g. clang in
tools/clang and so on) as an umbrella and order the commits according to
changes in llvm and its submodules.

Björn, this new version may well be able to handle the tasks you
outlined in December [2].

I've written some recipes as proposed additions to the GitHub migration
proposal [3].  If you have a different scenario, please comment there
and if it seems a like a common case I can add a recipe for it so we can
all benefit from the learning.

Much of the bugfixing work was the result of some artificial histories I
created to shake out problems.  I believe it is ready for some testing
in the wild.  If you do try it, please let me know how it worked for you
and any problems you run into.  I will try to fix them.  It's easiest if
you can provide me with a test repository showing the problem but even a
verbal description of what is happening can help.

I hope this tool is helpful to the community.

                             -David

[1] http://lists.llvm.org/pipermail/llvm-dev/2018-November/127704.html
[2] http://lists.llvm.org/pipermail/llvm-dev/2018-December/128620.html
[3] https://reviews.llvm.org/D56550