commit-tree: do not pay attention to commit.gpgsign

ba3c69a9 (commit: teach --gpg-sign option, 2011-10-05) introduced a
"signed commit" by teaching the --[no]-gpg-sign option and the
commit.gpgsign configuration variable to various commands that
create commits.

Teaching these to "git commit" and "git merge", both of which are
end-user facing Porcelain commands, was perfectly fine.  Allowing
the plumbing "git commit-tree" to suddenly change the behaviour to
surprise the scripts by paying attention to commit.gpgsign was not.

Among the in-tree scripts, filter-branch, quiltimport, rebase and
stash are the commands that run "commit-tree".  If any of these
wants to allow users to always sign every single commit, they should
offer their own configuration (e.g. "filterBranch.gpgsign") with an
option to disable signing (e.g. "git filter-branch --no-gpgsign").

Ignoring commit.gpgsign option _obviously_ breaks the backward
compatibility, but it is easy to follow the standard pattern in
scripts to honor whatever configuration variable they choose to
follow.  E.g.

	case $(git config --bool commit.gpgsign) in
	true) sign=-S ;;
	*) sign= ;;
	esac &&
	git commit-tree $sign ...whatever other args...

Do so to make sure that "git rebase" keeps paying attention to the
configuration variable, which unfortunately is a documented mistake.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-commit-tree.txt

@@ -59,8 +59,8 @@ OPTIONS
 	GPG-sign commit.
 
 --no-gpg-sign::
-	Countermand `commit.gpgSign` configuration variable that is
-	set to force each and every commit to be signed.
+	Do not GPG-sign commit, to countermand a `--gpg-sign` option
+	given earlier on the command line.
 
 
 Commit Information

builtin/commit-tree.c

@@ -33,10 +33,6 @@ static int commit_tree_config(const char *var, const char *value, void *cb)
 	int status = git_gpg_config(var, value, NULL);
 	if (status)
 		return status;
-	if (!strcmp(var, "commit.gpgsign")) {
-		sign_commit = git_config_bool(var, value) ? "" : NULL;
-		return 0;
-	}
 	return git_default_config(var, value, cb);
 }
 

git-rebase.sh

@@ -87,7 +87,10 @@ preserve_merges=
 autosquash=
 keep_empty=
 test "$(git config --bool rebase.autosquash)" = "true" && autosquash=t
-gpg_sign_opt=
+case "$(git config --bool commit.gpgsign)" in
+true)	gpg_sign_opt=-S ;;
+*)	gpg_sign_opt= ;;
+esac
 
 read_basic_state () {
 	test -f "$state_dir/head-name" &&

t/t7510-signed-commit.sh

@@ -45,12 +45,18 @@ test_expect_success GPG 'create signed commits' '
 	git tag seventh-signed &&
 
 	echo 8 >file && test_tick && git commit -a -m eighth -SB7227189 &&
-	git tag eighth-signed-alt
+	git tag eighth-signed-alt &&
+
+	# commit.gpgsign is still on but this must not be signed
+	git tag ninth-unsigned $(echo 9 | git commit-tree HEAD^{tree}) &&
+	# explicit -S of course must sign.
+	git tag tenth-signed $(echo 9 | git commit-tree -S HEAD^{tree})
 '
 
 test_expect_success GPG 'verify and show signatures' '
 	(
-		for commit in initial second merge fourth-signed fifth-signed sixth-signed seventh-signed
+		for commit in initial second merge fourth-signed \
+			fifth-signed sixth-signed seventh-signed tenth-signed
 		do
 			git verify-commit $commit &&
 			git show --pretty=short --show-signature $commit >actual &&
@@ -60,7 +66,8 @@ test_expect_success GPG 'verify and show signatures' '
 		done
 	) &&
 	(
-		for commit in merge^2 fourth-unsigned sixth-unsigned seventh-unsigned
+		for commit in merge^2 fourth-unsigned sixth-unsigned \
+			seventh-unsigned ninth-unsigned
 		do
 			test_must_fail git verify-commit $commit &&
 			git show --pretty=short --show-signature $commit >actual &&