[GSoC][PATCH v2] commit: add a commit.signOff config variable

[Chen Jingpiao <chenjingpiao@gmail.com>]

Add the commit.signOff configuration variable to use the -s or --signoff
option of git commit by default.

Convenience for those who prefer to add Signed-off-by line by the committer
instead of using format.signOff variable.

Signed-off-by: Chen Jingpiao <chenjingpiao@gmail.com>
---

Previous version of the patch:
[v1]: https://public-inbox.org/git/20180204020318.4363-1-chenjingpiao@gmail.com/

Changes in v2:
	* Update commit message: Move commentary explains to commit message.
	* Update test: Just test two combinations.
	Suggested-by: Eric Sunshine <sunshine@sunshineco.com>

 Documentation/config.txt     |  4 ++++
 Documentation/git-commit.txt |  2 ++
 builtin/commit.c             |  4 ++++
 t/t7501-commit.sh            | 10 ++++++++++
 4 files changed, 20 insertions(+)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 0e25b2c92..5dec3f0cb 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1303,6 +1303,10 @@ commit.gpgSign::
 	convenient to use an agent to avoid typing your GPG passphrase
 	several times.
 
+commit.signOff::
+	A boolean value which lets you enable the `-s/--signoff` option of
+	`git commit` by default. See linkgit:git-commit[1].
+
 commit.status::
 	A boolean to enable/disable inclusion of status information in the
 	commit message template when using an editor to prepare the commit
diff --git a/Documentation/git-commit.txt b/Documentation/git-commit.txt
index f970a4342..7a28ea765 100644
--- a/Documentation/git-commit.txt
+++ b/Documentation/git-commit.txt
@@ -166,6 +166,8 @@ The `-m` option is mutually exclusive with `-c`, `-C`, and `-F`.
 	the rights to submit this work under the same license and
 	agrees to a Developer Certificate of Origin
 	(see http://developercertificate.org/ for more information).
+	See the `commit.signOff` configuration variable in
+	linkgit:git-config[1].
 
 -n::
 --no-verify::
diff --git a/builtin/commit.c b/builtin/commit.c
index 4610e3d8e..324213254 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1548,6 +1548,10 @@ static int git_commit_config(const char *k, const char *v, void *cb)
 		sign_commit = git_config_bool(k, v) ? "" : NULL;
 		return 0;
 	}
+	if (!strcmp(k, "commit.signoff")) {
+		signoff = git_config_bool(k, v);
+		return 0;
+	}
 	if (!strcmp(k, "commit.verbose")) {
 		int is_bool;
 		config_commit_verbose = git_config_bool_or_int(k, v, &is_bool);
diff --git a/t/t7501-commit.sh b/t/t7501-commit.sh
index fa61b1a4e..adaaeea5b 100755
--- a/t/t7501-commit.sh
+++ b/t/t7501-commit.sh
@@ -505,6 +505,16 @@ Myfooter: x" &&
 	test_cmp expected actual
 '
 
+test_expect_success 'commit.signoff=true & --signoff omitted' '
+	git -c commit.signoff=true commit --allow-empty -m x &&
+	git log -1 --format=%B | grep ^Signed-off-by:
+'
+
+test_expect_success 'commit.signoff=true & --no-signoff' '
+	git -c commit.signoff=true commit --allow-empty -m x --no-signoff &&
+	! git log -1 --format=%B | grep ^Signed-off-by:
+'
+
 test_expect_success 'multiple -m' '
 
 	>negative &&
-- 
2.16.1.70.g5ccd54536