docs: remove Documentation/dontdiff

The dontdiff file is a relic from the pre-Git era that has little use now.
It has entries (parse.c, for example) that will mask real changes to kernel
source files.  There are all kinds of entries for files we do not create
anymore.  Rather than try to fix it up, simply remove it.

Update the kernel documentation (and translations) to remove references to
this file.  There is an ancient Japanese translation of SubmittingPatches
that I am unable to update; that really needs a thorough redo.

Message-ID: <87y12m1zk4.fsf@trenco.lwn.net>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Author: Jonathan Corbet

Documentation/dontdiff

@@ -191,11 +191,6 @@ change to a revision control system.  It will be followed by:
    option to diff will associate function names with changes, making the
    resulting patch easier for others to read.
 
-You should avoid including changes to irrelevant files (those generated by
-the build process, for example, or editor backup files) in the patch.  The
-file "dontdiff" in the Documentation directory can help in this regard;
-pass it to diff with the "-X" option.
-
 The tags already briefly mentioned above are used to provide insights how
 the patch came into being. They are described in detail in the
 :ref:`Documentation/process/submitting-patches.rst <submittingpatches>`

Documentation/process/5.Posting.rst

@@ -208,11 +208,6 @@ di commit in un sistema di controllo di versione.  Sarà seguito da:
    l'opzione "-p" assocerà alla modifica il nome della funzione alla quale
    si riferisce, rendendo il risultato più facile da leggere per gli altri.
 
-Dovreste evitare di includere nelle patch delle modifiche per file
-irrilevanti (quelli generati dal processo di generazione, per esempio, o i file
-di backup del vostro editor).  Il file "dontdiff" nella cartella Documentation
-potrà esservi d'aiuto su questo punto; passatelo a diff con l'opzione "-X".
-
 Le etichette sopracitate danno un'idea di come una patch prende vita e sono
 descritte nel dettaglio nel documento
 :ref:`Documentation/translations/it_IT/process/submitting-patches.rst <it_submittingpatches>`.

Documentation/translations/it_IT/process/5.Posting.rst

@@ -146,10 +146,6 @@
  - 补丁本身，采用统一的（“-u”）补丁格式。使用“-p”选项来diff将使函数名与
    更改相关联，从而使结果补丁更容易被其他人读取。
 
-您应该避免在补丁中包括与更改不相关文件（例如，构建过程生成的文件或编辑器
-备份文件）。文档目录中的“dontdiff”文件在这方面有帮助；使用“-X”选项将
-其传递给diff。
-
 上面提到的标签（tag）用于描述各种开发人员如何与这个补丁的开发相关联。
 :ref:`Documentation/translations/zh_CN/process/submitting-patches.rst <cn_submittingpatches>`
 文档中对它们进行了详细描述；下面是一个简短的总结。每一行的格式如下：

Documentation/translations/zh_CN/process/5.Posting.rst

@@ -149,10 +149,6 @@
  - 補丁本身，採用統一的（“-u”）補丁格式。使用“-p”選項來diff將使函數名與
    更改相關聯，從而使結果補丁更容易被其他人讀取。
 
-您應該避免在補丁中包括與更改不相關文件（例如，構建過程生成的文件或編輯器
-備份文件）。文檔目錄中的“dontdiff”文件在這方面有幫助；使用“-X”選項將
-其傳遞給diff。
-
 上面提到的標籤（tag）用於描述各種開發人員如何與這個補丁的開發相關聯。
 :ref:`Documentation/translations/zh_CN/process/submitting-patches.rst <tw_submittingpatches>`
 文檔中對它們進行了詳細描述；下面是一個簡短的總結。每一行的格式如下：