rebase: add --allow-empty-message option

This option allows commits with empty commit messages to be rebased,
matching the same option in git-commit and git-cherry-pick. While empty
log messages are frowned upon, sometimes one finds them in older
repositories (e.g. translated from another VCS [0]), or have other
reasons for desiring them. The option is available in git-commit and
git-cherry-pick, so it is natural to make other git tools play nicely
with them. Adding this as an option allows the default to be "give the
user a chance to fix", while not interrupting the user's workflow
otherwise [1].

  [0]: https://stackoverflow.com/q/8542304
  [1]: https://public-inbox.org/git/7vd33afqjh.fsf@alter.siamese.dyndns.org/

To implement this, add a new --allow-empty-message flag. Then propagate
it to all calls of 'git commit', 'git cherry-pick', and 'git rebase--helper'
within the rebase scripts.

Signed-off-by: Genki Sky <sky@genki.is>
Reviewed-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/t/t3405-rebase-malformed.sh b/t/t3405-rebase-malformed.sh
index ff8c360cd5..cb7c6de84a 100755
--- a/t/t3405-rebase-malformed.sh
+++ b/t/t3405-rebase-malformed.sh
@@ -3,6 +3,7 @@
 test_description='rebase should handle arbitrary git message'
 
 . ./test-lib.sh
+. "$TEST_DIRECTORY"/lib-rebase.sh
 
 cat >F <<\EOF
 This is an example of a commit log message
@@ -25,6 +26,7 @@ test_expect_success setup '
 	test_tick &&
 	git commit -m "Initial commit" &&
 	git branch diff-in-message &&
+	git branch empty-message-merge &&
 
 	git checkout -b multi-line-subject &&
 	cat F >file2 &&
@@ -45,6 +47,11 @@ test_expect_success setup '
 
 	git cat-file commit HEAD | sed -e "1,/^\$/d" >G0 &&
 
+	git checkout empty-message-merge &&
+	echo file3 >file3 &&
+	git add file3 &&
+	git commit --allow-empty-message -m "" &&
+
 	git checkout master &&
 
 	echo One >file1 &&
@@ -69,4 +76,20 @@ test_expect_success 'rebase commit with diff in message' '
 	test_cmp G G0
 '
 
+test_expect_success 'rebase -m commit with empty message' '
+	test_must_fail git rebase -m master empty-message-merge &&
+	git rebase --abort &&
+	git rebase -m --allow-empty-message master empty-message-merge
+'
+
+test_expect_success 'rebase -i commit with empty message' '
+	git checkout diff-in-message &&
+	set_fake_editor &&
+	test_must_fail env FAKE_COMMIT_MESSAGE=" " FAKE_LINES="reword 1" \
+		git rebase -i HEAD^ &&
+	git rebase --abort &&
+	FAKE_COMMIT_MESSAGE=" " FAKE_LINES="reword 1" \
+		git rebase -i --allow-empty-message HEAD^
+'
+
 test_done