From: Phillip Wood <redacted>

Rebase is implemented with two different backends - 'apply' and
'merge' each of which support a different set of options. In
particular the apply backend supports a number of options implemented
by 'git am' that are not implemented in the merge backend. This means
that the available options are different depending on which backend is
used which is confusing. This patch adds support for the --ignore-date
option to the merge backend. This option uses the current time as the
author date rather than reusing the original author date when
rewriting commits. We take care to handle the combination of
--ignore-date and --committer-date-is-author-date in the same way as
the apply backend.

Original-patch-by: Rohit Ashiwal [off-list ref]
Signed-off-by: Phillip Wood <redacted>
---
 Documentation/git-rebase.txt   |  7 ++--
 builtin/rebase.c               | 13 ++++---
 sequencer.c                    | 66 +++++++++++++++++++++++++++-------
 sequencer.h                    |  1 +
 t/t3436-rebase-more-options.sh | 56 +++++++++++++++++++++++++++++
 5 files changed, 123 insertions(+), 20 deletions(-)

 [...]

diff --git a/t/t3436-rebase-more-options.sh b/t/t3436-rebase-more-options.sh
index 50a63d8ebe..0ede2b8900 100755
--- a/t/t3436-rebase-more-options.sh
+++ b/t/t3436-rebase-more-options.sh

@@ -108,6 +108,62 @@ test_expect_success '--committer-date-is-author-date works when committing confl
 	test_ctime_is_atime -1
 '
 
+# Checking for +0000 in the author date is sufficient since the
+# default timezone is UTC but the timezone used while committing is
+# +0530. The inverted logic in the grep is necessary to check all the
+# author dates in the file.
+test_ctime_is_ignored () {
+	git log $1 --format=%ai >authortime &&
+	! grep -v +0000 authortime
+}