[clang] [Clang] [NFC] Add "human" diagnostic argument format (PR #115835)

[via cfe-commits]

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@@ -315,6 +315,18 @@ Description:
   than ``1`` are not supported.  This formatter is currently hard-coded to use
   English ordinals.
 
+**"human" format**
+
+Example:
+  ``"total size is %human0 bytes"``
+Class:
+  Integers
+Description:
+  This is a formatter which represents the argument number in a human readable
+  format: the value ``123`` stays ``123``, ``12345`` becomes ``12.34k``,
+  ``6666666` becomes ``6.67M``, and so on for 'G' and 'T'.  Values less than
+  ``0`` are not supported.
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Sirraide wrote:

> Values less than ``0`` are not supported.

Are they really not? With how everything is set up a the moment, wouldn’t e.g. `-10000` just become `-10k`, which is fine imo?

https://github.com/llvm/llvm-project/pull/115835