Subject: Re: [PATCH v3] merge: add a --signoff flag.

From: Junio C Hamano <[email-masked]>
Date: Tue, 25 Jul 2017 11:41:33 -0700

Łukasz Gryglicki <[email-masked]> writes:

> Some projects require every commit to be signed off.
> Our workflow is to create feature branches and require every commit to
> be signed off. When feature is finally approved we need to merge it into
> master. Merge itself is usually trivial and is done by
> `git merge origin/master`.
>
> Unfortunatelly `merge` command have no --signoff
> flag, so we need to either add signoff line manually or use
> `git commit --amend -s` after the merge.

Who are "we" in the above?  Certainly not the Git development
project who stands behind the log message.  I also find the first
paragraph overly verbose.  

Perhaps something like this instead?

    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=[email-masked]/T/#u

    Requested-by: Dan Kohn <[email-masked]>
    Signed-off-by: Łukasz Gryglicki <[email-masked]>

Notice that I updated your s-o-b line in the above illustration
because we prefer to see the same name as patch author (which is
usually taken from your e-mail From: header) there.

> +--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 submit this work under the same license and
> +	agrees to a Developer Certificate of Origin
> +	(see http://developercertificate.org/ for more information).

This is taken verbatim from Documentation/git-commit.txt and "this
work" in that context is entirely sensible, but it is not quite
clear what it means in the context of "git merge".

> 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))

The invocation of the editor comes after this post-context, and the
new code seems to sit at the right place.  Good.

> diff --git a/t/t7614-merge-signoff.sh b/t/t7614-merge-signoff.sh
> new file mode 100755
> index 0000000000000..c1b8446f491dc
> --- /dev/null
> +++ b/t/t7614-merge-signoff.sh
> @@ -0,0 +1,69 @@
> +#!/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() {

Style: "test_setup () {" but see below.

> +	# Expected commit message after merge --signoff
> +	cat >expected-signed <<EOF &&
> +Merge branch 'master' into other-branch
> +
> +Signed-off-by: $(git var GIT_COMMITTER_IDENT | sed -e "s/>.*/>/")
> +EOF

Indenting the here-text with "<<-EOF" makes it easier to read, e.g.

	cat >expected-signed <<-EOF &&
	Merge branch 'master' into other-branch

	Signed-off-by: $(git var GIT_COMMITTER_IDENT | sed -e "s/>.*/>/")
	EOF

Likewise for the other one.

> +...
> +}

I do not see much point in making this a shell function.  I'd just
do all of the above in the first "test_expect_success 'setup'"
thing, if I were doing this patch.

> +
> +# Setup repository, files & feature branch
> +# This step must be run if You want to test 2,3 or 4
> +# Order of 2,3,4 is not important, but 1 must be run before
> +# For example `-r 1,4` or `-r 1,4,2 -v` etc
> +# But not `-r 2` or `-r 4,3,2,1`

That is pretty much the standard practice to require 'setup' to
always run; no need to waste 5 lines to document it.

> +test_expect_success 'setup' '
> +	test_setup
> +'
> +
> +# Test with --signoff flag

That can already be seen on the test title below.  Remove it?

> +test_expect_success 'git merge --signoff adds a sign-off line' '
> +...
> +test_expect_success 'git merge does not add a sign-off line' '
> +...
> +test_expect_success 'git merge --no-signoff flag cancels --signoff flag' '
> +...
> +'

They all look sensible thing to check.  We would also need to make
sure that the end user sees the S-o-b: prepopulated when the editor
is spawned, I would think, perhaps like (completely untested)

	write_script save-editor <<-\EOF &&
	cp "$1" "$1".saved
	EOF
	GIT_EDITOR=./save-editor git merge --signoff --no-signoff ... &&
 	... check the contents of the MERGE_MSG.saved file to 
	... ensure string Signed-off-by: appears (or does not
	... appear) here, e.g.
	test_i18ngrep ! "^Signed-off-by: " .git/MERGE_MSG.saved

Thanks.