[docs] use git diff instead of git format-patch

[AlexanderLanin]

Summary

Uploading output from git format-patch fails when version has more than 2 dots, e.g. git version 2.24.1.windows.2 which is currently recommended by e.g. GitExtensions or 2.24.1.rc on linux.

Phabricator complains with:

Diff Parse Exception: Expected a hunk header, like 'Index: /path/to/file.ext' (svn), 'Property changes on: /path/to/file.ext' (svn properties), 'commit 59bcc3ad6775562f845953cf01624225' (git show), 'diff --git' (git diff), '--- filename' (unified diff), or 'diff -r' (hg diff or patch).

        2318    .. _`https://reviews.llvm.org`: https://reviews.llvm.org
        2319    .. _Code Repository Browser: https://reviews.llvm.org/diffusion/
        2320    .. _Arcanist Quick Start: https://secure.phabricator.com/book/phabricator/article/arcanist_quick_start/
        2321    .. _Arcanist User Guide: https://secure.phabricator.com/book/phabricator/article/arcanist/
        2322    .. _llvm-reviews GitHub project: https://github.com/r4nt/llvm-reviews/
>>>     2323   -- 
        2324   2.24.1.windows.2
        2325

[AlexanderLanin]

The only difference is the git version in the end:

0001-docs-replace-git-format-patch-with-git-diff.git-2.17.1.patch100 KBDownload

0001-docs-replace-git-format-patch-with-git-diff.git-2.24.1.windows.2.patch100 KBDownload

[gbedwell]

In D72374#1809115, @AlexanderLanin wrote:

The only difference is the git version in the end:

I previously reported this here: https://bugs.llvm.org/show_bug.cgi?id=37834

[AlexanderLanin]

I guess it's not so easy to fix as you reported this 1,5 years ago. That's an even better reason to update the documentation to work around the issue.

[AlexanderLanin]

Hi, could anyone provide feedback here?
Windows and RC Versions of git do not work with format-patch.

Maybe that's not the majority of users that are affected, but still.
For me it was relevant since I use Windows GitExtensions for the GUI + WSL for the rest.
I personally see more and more people using similar setups.

[AlexanderLanin]

*ping*

[probinson]

I normally use git diff even on Linux. If someone comes up with a reason why format-patch is better for generating a diff for Phab, they can add it back in.
LGTM

llvm/docs/Phabricator.rst

62–64

While you're here, please delete the svn line.

[AlexanderLanin]

Rebased. Solves the svn issue as it's gone in the meantime.

Could someone commit this as I cannot?
Alexander Lanin <[e-mail]>

[AlexanderLanin]

*ping*

[probinson]

In D72374#1915798, @AlexanderLanin wrote:

Rebased. Solves the svn issue as it's gone in the meantime.

Could someone commit this as I cannot?
Alexander Lanin <[e-mail]>

Sorry--done now, llvmorg-11-init-7559-g6668453dd25

[ps-19]

This comment was removed by ps-19.

llvm/docs/DeveloperPolicy.rst

#. Make your patch against git master, not a branch, and not an old version
    of LLVM.  This makes it easy to apply the patch.  For information on how to
    clone from git, please see the :ref:`Getting Started Guide
    <checkout>`.
 
 #. Similarly, patches should be submitted soon after they are generated.  Old
    patches may not apply correctly if the underlying code changes between the
    time the patch was created and the time it is applied.
 
-#. Patches should be made with ``git format-patch``, or similar. If you use a
+#. Patches should be made with ``git format-patch``, or similar (see special
+   commands for `Requesting Phabricator review via the web interface
+   <Phabricator.html#phabricator-request-review-web>`_ ). If you use a
    different tool, make sure it uses the ``diff -u`` format and that it
    doesn't contain clutter which makes it hard to read.
 
 Once your patch is ready, submit it by emailing it to the appropriate project's
 commit mailing list (or commit it directly if applicable). Alternatively, some
 patches get sent to the project's development list or component of the LLVM bug
 tracker, but the commit list is the primary place for reviews and should
 generally be preferred.

llvm/docs/GettingStarted.rst

 
 We don't currently accept github pull requests, so you'll need to send patches
 either via emailing to llvm-commits, or, preferably, via :ref:`Phabricator
 <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/master`` branch, and doesn't contain merges. Once you have that, you
-can use ``git show`` or ``git format-patch`` to output the diff, and attach it
-to a Phabricator review (or to an email message).
+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:
 
 .. code-block:: console
 
   % arc diff HEAD~1
 

llvm/docs/Phabricator.rst

 will automatically send a diff with a smaller context in the review
 email, but having the full file in the web interface will help the
 reviewer understand your code.
 
 To get a full diff, use one of the following commands (or just use Arcanist
 to upload your patch):
 
 * ``git show HEAD -U999999 > mypatch.patch``
-* ``git format-patch -U999999 @{u}``
+* ``git diff -U999999 @{u} > mypatch.patch``
+* ``git diff HEAD~1 -U999999 > mypatch.patch``
 
 Before uploading your patch, please make sure it is formatted properly, as
 described in :ref:`How to Submit a Patch <format patches>`.
 
 To upload a new patch:
 
 * Click *Differential*.
 * Click *+ Create Diff*.
 * Paste the text diff or browse to the patch file. Click *Create Diff*.