[PATCH v2] commit: document that $command.signoff will not be added

[Junio C Hamano <gitster@pobox.com>]

Every now and then we see this coming up on the list.  Let's help
new contributors who are not aware of past discussions by clearly
documenting our past consensus.

Helped-by: brian m. carlson <sandals@crustytoothpaste.net>
Helped-by: Elijah Newren <newren@gmail.com>
Helped-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 * The text is from Elijah and Johannes this round; I am merely
   playing a copybot.

 Documentation/gitfaq.adoc         | 19 +++++++++++++++++++
 Documentation/signoff-option.adoc |  4 ++++
 2 files changed, 23 insertions(+)

diff --git c/Documentation/gitfaq.adoc w/Documentation/gitfaq.adoc
index f2917d142c..0e40befb77 100644
--- c/Documentation/gitfaq.adoc
+++ w/Documentation/gitfaq.adoc
@@ -83,6 +83,25 @@ Windows would be the configuration `"C:\Program Files\Vim\gvim.exe" --nofork`,
 which quotes the filename with spaces and specifies the `--nofork` option to
 avoid backgrounding the process.
 
+[[sign-off]]
+Why not have `commit.signoff` and other configuration variables?::
+	Git intentionally does not (and will not) provide a
+	configuration variable, such as `commit.signoff`, to
+	automatically add `--signoff` by default.  The reason is to
+	protect the legal and intentional significance of a sign-off.
+	If there were more automated and widely publicized ways for
+	sign-offs to be appended, it would become easier for someone
+	to argue later that a "Signed-off-by" trailer was just added
+	out of habit or by automation, without the committer's full
+	awareness or intent to certify their agreement with the
+	Developer Certificate of Origin (DCO) or a similar statement.
+	This could undermine the sign-off’s credibility in legal or
+	contractual situations.
++
+There exists `format.signoff`, but that is a historical mistake, and
+it is not an excuse to pile on more mistakes of the same kind on top.
+
+
 Credentials
 -----------
 
diff --git c/Documentation/signoff-option.adoc w/Documentation/signoff-option.adoc
index cddfb225d1..9a80d60f1b 100644
--- c/Documentation/signoff-option.adoc
+++ w/Documentation/signoff-option.adoc
@@ -16,3 +16,7 @@ endif::git-commit[]
 +
 The `--no-signoff` option can be used to countermand an earlier `--signoff`
 option on the command line.
++
+Git does not (and will not) have a configuration variable to enable
+the `--signoff` command line option by default; see the
+`commit.signoff` entry in the gitfaq for more details.