Merge branch 'jc/conf-var-doc' into maint

Longstanding configuration variable naming rules has been added to
the documentation.

* jc/conf-var-doc:
CodingGuidelines: describe naming rules for configuration variables
config.txt: mark deprecated variables more prominently
config.txt: clarify that add.ignore-errors is deprecated

diff --cc Documentation/config.txt
index 04e2a71687922bbf78a493df6ca6dc5730359eb1,8a76d1dc2af13f364f03b6c582a4d94e419f33f0..b22a7a7ff52f124dce2e2cb16040bffaeee391cb
--- 1/Documentation/config.txt
--- 2/Documentation/config.txt
+++ b/Documentation/config.txt
@@@ -2332,12 -2269,10 +2331,12 @@@ sendemail.smtpserverport:
  sendemail.smtpserveroption::
  sendemail.smtpuser::
  sendemail.thread::
 +sendemail.transferencoding::
  sendemail.validate::
 +sendemail.xmailer::
        See linkgit:git-send-email[1] for description.
  
- sendemail.signedoffcc::
+ sendemail.signedoffcc (deprecated)::
        Deprecated alias for 'sendemail.signedoffbycc'.
  
  showbranch.default::