docs: Document workaround for arcanist failures

[smeenai]

LGTM, thanks.

[smeenai]

Would we want to put up the commit in a fork that we control, so that we're not relying on someone else's fork (which may go away in the future)?

[ctetreau]

In D110976#3037605, @smeenai wrote:

Would we want to put up the commit in a fork that we control, so that we're not relying on someone else's fork (which may go away in the future)?

+1

Ideally, a fork could live in the LLVM github org with this patch applied.

[tstellar]

We discussed this at the last board meeting and decided that we don't want to be hosting non-LLVM projects in our GitHub organization. We can always update the docs if this workaround stops working.

[mehdi_amini]

In D110976#3046911, @tstellar wrote:

We discussed this at the last board meeting and decided that we don't want to be hosting non-LLVM projects in our GitHub organization. We can always update the docs if this workaround stops working.

This is weird, we already decided to host the repo for our own fork of Phabricator: https://github.com/llvm/phabricator

[tstellar]

In D110976#3047077, @mehdi_amini wrote:

In D110976#3046911, @tstellar wrote:

We discussed this at the last board meeting and decided that we don't want to be hosting non-LLVM projects in our GitHub organization. We can always update the docs if this workaround stops working.

This is weird, we already decided to host the repo for our own fork of Phabricator: https://github.com/llvm/phabricator

I don't think anyone was aware of this, I will raise the question again.

In the meantime, I'm going to commit this so that we have a documented solution.

[ctetreau]

Any news on this? As @mehdi_amini mentions, we have a fork. I would think that the ideal solution is to just merge that PR into our fork, then update the instructions to say to use our repo for arcanist. If our fork of phabricator is not long for this world, I don't think this would make getting rid of it in the future significantly harder.

Did you get any clarification on this issue @tstellar?

[mehdi_amini]

In the meantime, I'm going to commit this so that we have a documented solution.

I pushed this in 509fe20fbca767a65b9c27750ea9d372ed2ab05a

In D110976#3061904, @ctetreau wrote:

Any news on this? As @mehdi_amini mentions, we have a fork.

Sorry: we only have a fork for the server side Phabricator software. We'd have to fork the arcanist repo as well.

[ctetreau]

OK, thanks for the update!

llvm/docs/GettingStarted.rst

 <phabricator-reviews>`.
 
 You'll generally want to make sure your branch has a single commit,
 corresponding to the review you wish to send, up-to-date with the upstream
 ``origin/main`` branch, and doesn't contain merges. Once you have that, you
 can start `a Phabricator review <Phabricator.html>`_ (or use ``git show`` or
 ``git format-patch`` to output the diff, and attach it to an email message).
 
-However, using the "Arcanist" tool is often easier. After `installing
-arcanist`_, you can upload the latest commit using:
+However, using the "Arcanist" tool is often easier. After `installing arcanist`_, you
+will also need to apply a fix to your arcanist repo in order to submit a patch:
+
+.. code-block:: console
+
+  % cd arcanist
+  % git fetch https://github.com/rashkov/arcanist update_cacerts
+  % git cherry-pick e3659d43d8911e91739f3b0c5935598bceb859aa
+
+Once this is all done, you can upload the latest commit using:
 
 .. code-block:: console
 
   % arc diff HEAD~1
 
 Additionally, before sending a patch for review, please also try to ensure it's
 formatted properly. We use ``clang-format`` for this, which has git integration
 through the ``git-clang-format`` script. On some systems, it may already be