[PATCH v4] merge: add a --signoff flag.

["Łukasz Gryglicki" <lukaszgryglicki@o2.pl>]

Some projects require every commit, even merges, to be signed off [*1*].
Because "git merge" does not have a "--signoff"
option like "git commit" does, the user needs to add one
manually when the command presents an editor to describe the
merge, or later use "git commit --amend --signoff".

Help developers of these projects by teaching "--signoff" option to "git merge".

*1*
https://public-inbox.org/git/CAHv71zK5SqbwrBFX=a8-DY9H3KT4FEyMgv__p2gZzNr0WUAPUw@mail.gmail.com/T/#u

Requested-by: Dan Kohn <dan@linuxfoundation.org>
Signed-off-by: Łukasz Gryglicki <lukaszgryglicki@o2.pl>
---
 Documentation/git-merge.txt |  8 +++++
 builtin/merge.c             |  4 +++
 t/t7614-merge-signoff.sh    | 88 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 100 insertions(+)
 create mode 100755 t/t7614-merge-signoff.sh

diff --git a/Documentation/git-merge.txt b/Documentation/git-merge.txt
index 04fdd8cf086db..630cb4b7f90d7 100644
--- a/Documentation/git-merge.txt
+++ b/Documentation/git-merge.txt
@@ -64,6 +64,14 @@ OPTIONS
 -------
 include::merge-options.txt[]
 
+--signoff::
+	Add Signed-off-by line by the committer at the end of the commit
+	log message.  The meaning of a signoff depends on the project,
+	but it typically certifies that committer has
+	the rights to merge work under the same license and
+	agrees to a Developer Certificate of Origin
+	(see http://developercertificate.org/ for more information).
+
 -S[<keyid>]::
 --gpg-sign[=<keyid>]::
 	GPG-sign the resulting merge commit. The `keyid` argument is
diff --git a/builtin/merge.c b/builtin/merge.c
index 900bafdb45d0b..78c36e9bf353b 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -70,6 +70,7 @@ static int continue_current_merge;
 static int allow_unrelated_histories;
 static int show_progress = -1;
 static int default_to_upstream = 1;
+static int signoff;
 static const char *sign_commit;
 
 static struct strategy all_strategy[] = {
@@ -233,6 +234,7 @@ static struct option builtin_merge_options[] = {
 	{ OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
 	  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
 	OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
+	OPT_BOOL(0, "signoff", &signoff, N_("add Signed-off-by:")),
 	OPT_END()
 };
 
@@ -763,6 +765,8 @@ static void prepare_to_commit(struct commit_list *remoteheads)
 	strbuf_addch(&msg, '\n');
 	if (0 < option_edit)
 		strbuf_commented_addf(&msg, _(merge_editor_comment), comment_line_char);
+	if (signoff)
+		append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
 	write_file_buf(git_path_merge_msg(), msg.buf, msg.len);
 	if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
 			    git_path_merge_msg(), "merge", NULL))
diff --git a/t/t7614-merge-signoff.sh b/t/t7614-merge-signoff.sh
new file mode 100755
index 0000000000000..823d840d423df
--- /dev/null
+++ b/t/t7614-merge-signoff.sh
@@ -0,0 +1,88 @@
+#!/bin/sh
+
+test_description='git merge --signoff
+
+This test runs git merge --signoff and makes sure that it works.
+'
+
+. ./test-lib.sh
+
+# Setup test files
+test_setup () {
+  # Expected commit message after merge --signoff
+  printf "Merge branch 'master' into other-branch\n\n" >expected-signed &&
+  printf "Signed-off-by: $(git var GIT_COMMITTER_IDENT | sed -e "s/>.*/>/")\n" >>expected-signed &&
+
+  # Expected commit message after merge without --signoff (or with --no-signoff)
+  echo "Merge branch 'master' into other-branch" >expected-unsigned &&
+
+  # Initial commit and feature branch to merge master into it.
+  git commit --allow-empty -m "Initial empty commit" &&
+  git checkout -b other-branch &&
+  test_commit other-branch file1 1
+}
+
+# Create fake editor that just copies file
+create_fake_editor () {
+  echo 'cp "$1" "$1.saved"' | write_script save-editor
+}
+
+test_expect_success 'setup' '
+  test_setup && create_fake_editor
+'
+
+test_expect_success 'git merge --signoff adds a sign-off line' '
+  git checkout master &&
+  test_commit master-branch-2 file2 2 &&
+  git checkout other-branch &&
+  git merge master --signoff --no-edit &&
+  git cat-file commit HEAD | sed -e "1,/^\$/d" >actual &&
+  test_cmp expected-signed actual
+'
+
+test_expect_success 'git merge does not add a sign-off line' '
+  git checkout master &&
+  test_commit master-branch-3 file3 3 &&
+  git checkout other-branch &&
+  git merge master --no-edit &&
+  git cat-file commit HEAD | sed -e "1,/^\$/d" >actual &&
+  test_cmp expected-unsigned actual
+'
+
+test_expect_success 'git merge --no-signoff flag cancels --signoff flag' '
+  git checkout master &&
+  test_commit master-branch-4 file4 4 &&
+  git checkout other-branch &&
+  git merge master --no-edit --signoff --no-signoff &&
+  git cat-file commit HEAD | sed -e "1,/^\$/d" >actual &&
+  test_cmp expected-unsigned actual
+'
+
+test_expect_success 'git merge --signoff adds S-o-b line in commit message editor' '
+  git checkout master &&
+  test_commit master-branch-5 file5 5 &&
+  git checkout other-branch &&
+  GIT_EDITOR=./save-editor git merge master -m "My Message" --edit --signoff &&
+  test_i18ngrep "^My Message" .git/MERGE_MSG.saved &&
+  test_i18ngrep "^Signed-off-by: " .git/MERGE_MSG.saved
+'
+
+test_expect_success 'git merge --no-signoff does not add S-o-b line in commit message editor' '
+  git checkout master &&
+  test_commit master-branch-6 file6 6 &&
+  git checkout other-branch &&
+  GIT_EDITOR=./save-editor git merge master -m "My Message" --edit --no-signoff &&
+  test_i18ngrep "^My Message" .git/MERGE_MSG.saved &&
+  test_i18ngrep ! "^Signed-off-by: " .git/MERGE_MSG.saved
+'
+
+test_expect_success 'git merge --no-signoff cancels --signoff flag in commit message editor' '
+  git checkout master &&
+  test_commit master-branch-7 file7 7 &&
+  git checkout other-branch &&
+  GIT_EDITOR=./save-editor git merge master -m "My Message" --edit --signoff --no-signoff &&
+  test_i18ngrep "^My Message" .git/MERGE_MSG.saved &&
+  test_i18ngrep ! "^Signed-off-by: " .git/MERGE_MSG.saved
+'
+
+test_done

--
https://github.com/git/git/pull/390