[PATCH] commit-tree: add missing --gpg-sign flag

[Brandon Richardson <brandon1024.br@gmail.com>]

Add --gpg-sign option in commit-tree, which was documented, but not
implemented, in 55ca3f99ae.

Signed-off-by: Brandon Richardson <brandon1024.br@gmail.com>
---

Thanks Martin for the tips and suggestions!

 builtin/commit-tree.c    | 8 +++++++-
 t/t7510-signed-commit.sh | 4 +++-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/builtin/commit-tree.c b/builtin/commit-tree.c
index 9ec36a82b..a51b2c8d7 100644
--- a/builtin/commit-tree.c
+++ b/builtin/commit-tree.c
@@ -66,7 +66,13 @@ int cmd_commit_tree(int argc, const char **argv, const char *prefix)
 			continue;
 		}
 
-		if (skip_prefix(arg, "-S", &sign_commit))
+		if(!strcmp(arg, "--gpg-sign")) {
+		    skip_prefix(arg, "--gpg-sign", &sign_commit);
+		    continue;
+		}
+
+		if (skip_prefix(arg, "-S", &sign_commit) ||
+			skip_prefix(arg, "--gpg-sign=", &sign_commit))
 			continue;
 
 		if (!strcmp(arg, "--no-gpg-sign")) {
diff --git a/t/t7510-signed-commit.sh b/t/t7510-signed-commit.sh
index 86d3f93fa..efc136eaf 100755
--- a/t/t7510-signed-commit.sh
+++ b/t/t7510-signed-commit.sh
@@ -51,7 +51,9 @@ test_expect_success GPG 'create signed commits' '
 	# 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})
+	git tag tenth-signed $(echo 10 | git commit-tree -S HEAD^{tree})
+	# --gpg-sign must sign.
+	git tag eleventh-signed $(echo 11 | git commit-tree --gpg-sign HEAD^{tree})
 '
 
 test_expect_success GPG 'verify and show signatures' '
-- 
2.20.1