From 5b88a0b4d42c8d19feb63fde2f0c68a8bbe5dc1d Mon Sep 17 00:00:00 2001
From: Rohit Ashiwal <rohit.ashiwal265@gmail.com>
Date: Wed, 27 May 2020 18:33:52 +0100
Subject: [PATCH 1/5] rebase -i: add --ignore-whitespace flag

Rebase is implemented with two different backends - 'apply' and 'merge'
each of which support a different set of options. In particuar the apply
backend supports a number of options implemented by 'git am' that are
not available to the merge backend. As part of an on going effort to
remove the apply backend this patch adds support for the
--ignore-whitespace option to the merge backend. This option treats
lines with only whitespace changes as unchanged and is implemented in
the merge backend by translating it to -Xignore-space-change.

Signed-off-by: Rohit Ashiwal <rohit.ashiwal265@gmail.com>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-rebase.txt           | 19 +++++-
 builtin/rebase.c                       | 19 ++++--
 t/t3422-rebase-incompatible-options.sh |  1 -
 t/t3436-rebase-more-options.sh         | 86 ++++++++++++++++++++++++++
 4 files changed, 118 insertions(+), 7 deletions(-)
 create mode 100755 t/t3436-rebase-more-options.sh

diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index f7a6033607..b003784f01 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -422,8 +422,23 @@ your branch contains commits which were dropped, this option can be used
 with `--keep-base` in order to drop those commits from your branch.
 
 --ignore-whitespace::
+	Ignore whitespace differences when trying to reconcile
+differences. Currently, each backend implements an approximation of
+this behavior:
++
+apply backend: When applying a patch, ignore changes in whitespace in
+context lines. Unfortunately, this means that if the "old" lines being
+replaced by the patch differ only in whitespace from the existing
+file, you will get a merge conflict instead of a successful patch
+application.
++
+merge backend: Treat lines with only whitespace changes as unchanged
+when merging. Unfortunately, this means that any patch hunks that were
+intended to modify whitespace and nothing else will be dropped, even
+if the other side had no changes that conflicted.
+
 --whitespace=<option>::
-	These flags are passed to the 'git apply' program
+	This flag is passed to the 'git apply' program
 	(see linkgit:git-apply[1]) that applies the patch.
 	Implies --apply.
 +
@@ -572,7 +587,6 @@ The following options:
  * --apply
  * --committer-date-is-author-date
  * --ignore-date
- * --ignore-whitespace
  * --whitespace
  * -C
 
@@ -598,6 +612,7 @@ In addition, the following pairs of options are incompatible:
  * --preserve-merges and --signoff
  * --preserve-merges and --rebase-merges
  * --preserve-merges and --empty=
+ * --preserve-merges and --ignore-whitespace
  * --keep-base and --onto
  * --keep-base and --root
 
diff --git a/builtin/rebase.c b/builtin/rebase.c
index 27a07d4e78..5d8e117276 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -86,6 +86,7 @@ struct rebase_options {
 	int signoff;
 	int allow_rerere_autoupdate;
 	int autosquash;
+	int ignore_whitespace;
 	char *gpg_sign_opt;
 	int autostash;
 	char *cmd;
@@ -108,6 +109,7 @@ struct rebase_options {
 
 static struct replay_opts get_replay_opts(const struct rebase_options *opts)
 {
+	struct strbuf strategy_buf = STRBUF_INIT;
 	struct replay_opts replay = REPLAY_OPTS_INIT;
 
 	replay.action = REPLAY_INTERACTIVE_REBASE;
@@ -126,14 +128,20 @@ static struct replay_opts get_replay_opts(const struct rebase_options *opts)
 	replay.reschedule_failed_exec = opts->reschedule_failed_exec;
 	replay.gpg_sign = xstrdup_or_null(opts->gpg_sign_opt);
 	replay.strategy = opts->strategy;
+
 	if (opts->strategy_opts)
-		parse_strategy_opts(&replay, opts->strategy_opts);
+		strbuf_addstr(&strategy_buf, opts->strategy_opts);
+	if (opts->ignore_whitespace)
+		strbuf_addstr(&strategy_buf, " --ignore-space-change");
+	if (strategy_buf.len)
+		parse_strategy_opts(&replay, strategy_buf.buf);
 
 	if (opts->squash_onto) {
 		oidcpy(&replay.squash_onto, opts->squash_onto);
 		replay.have_squash_onto = 1;
 	}
 
+	strbuf_release(&strategy_buf);
 	return replay;
 }
 
@@ -539,6 +547,8 @@ int cmd_rebase__interactive(int argc, const char **argv, const char *prefix)
 	argc = parse_options(argc, argv, prefix, options,
 			builtin_rebase_interactive_usage, PARSE_OPT_KEEP_ARGV0);
 
+	opts.strategy_opts = xstrdup_or_null(opts.strategy_opts);
+
 	if (!is_null_oid(&squash_onto))
 		opts.squash_onto = &squash_onto;
 
@@ -991,6 +1001,8 @@ static int run_am(struct rebase_options *opts)
 	am.git_cmd = 1;
 	argv_array_push(&am.args, "am");
 
+	if (opts->ignore_whitespace)
+		argv_array_push(&am.args, "--ignore-whitespace");
 	if (opts->action && !strcmp("continue", opts->action)) {
 		argv_array_push(&am.args, "--resolved");
 		argv_array_pushf(&am.args, "--resolvemsg=%s", resolvemsg);
@@ -1495,9 +1507,6 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			PARSE_OPT_NOARG, NULL, REBASE_DIFFSTAT },
 		OPT_BOOL(0, "signoff", &options.signoff,
 			 N_("add a Signed-off-by: line to each commit")),
-		OPT_PASSTHRU_ARGV(0, "ignore-whitespace", &options.git_am_opts,
-				  NULL, N_("passed to 'git am'"),
-				  PARSE_OPT_NOARG),
 		OPT_PASSTHRU_ARGV(0, "committer-date-is-author-date",
 				  &options.git_am_opts, NULL,
 				  N_("passed to 'git am'"), PARSE_OPT_NOARG),
@@ -1505,6 +1514,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 				  N_("passed to 'git am'"), PARSE_OPT_NOARG),
 		OPT_PASSTHRU_ARGV('C', NULL, &options.git_am_opts, N_("n"),
 				  N_("passed to 'git apply'"), 0),
+		OPT_BOOL(0, "ignore-whitespace", &options.ignore_whitespace,
+			 N_("ignore changes in whitespace")),
 		OPT_PASSTHRU_ARGV(0, "whitespace", &options.git_am_opts,
 				  N_("action"), N_("passed to 'git apply'"), 0),
 		OPT_BIT('f', "force-rebase", &options.flags,
diff --git a/t/t3422-rebase-incompatible-options.sh b/t/t3422-rebase-incompatible-options.sh
index 50e7960702..55ca46786d 100755
--- a/t/t3422-rebase-incompatible-options.sh
+++ b/t/t3422-rebase-incompatible-options.sh
@@ -61,7 +61,6 @@ test_rebase_am_only () {
 }
 
 test_rebase_am_only --whitespace=fix
-test_rebase_am_only --ignore-whitespace
 test_rebase_am_only --committer-date-is-author-date
 test_rebase_am_only -C4
 
diff --git a/t/t3436-rebase-more-options.sh b/t/t3436-rebase-more-options.sh
new file mode 100755
index 0000000000..fb5e747e86
--- /dev/null
+++ b/t/t3436-rebase-more-options.sh
@@ -0,0 +1,86 @@
+#!/bin/sh
+#
+# Copyright (c) 2019 Rohit Ashiwal
+#
+
+test_description='tests to ensure compatibility between am and interactive backends'
+
+. ./test-lib.sh
+
+. "$TEST_DIRECTORY"/lib-rebase.sh
+
+# This is a special case in which both am and interactive backends
+# provide the same output. It was done intentionally because
+# both the backends fall short of optimal behaviour.
+test_expect_success 'setup' '
+	git checkout -b topic &&
+	q_to_tab >file <<-\EOF &&
+	line 1
+	Qline 2
+	line 3
+	EOF
+	git add file &&
+	git commit -m "add file" &&
+	cat >file <<-\EOF &&
+	line 1
+	new line 2
+	line 3
+	EOF
+	git commit -am "update file" &&
+	git tag side &&
+
+	git checkout --orphan master &&
+	sed -e "s/^|//" >file <<-\EOF &&
+	|line 1
+	|        line 2
+	|line 3
+	EOF
+	git add file &&
+	git commit -m "add file" &&
+	git tag main
+'
+
+test_expect_success '--ignore-whitespace works with apply backend' '
+	cat >expect <<-\EOF &&
+	line 1
+	new line 2
+	line 3
+	EOF
+	test_must_fail git rebase --apply main side &&
+	git rebase --abort &&
+	git rebase --apply --ignore-whitespace main side &&
+	test_cmp expect file
+'
+
+test_expect_success '--ignore-whitespace works with merge backend' '
+	cat >expect <<-\EOF &&
+	line 1
+	new line 2
+	line 3
+	EOF
+	test_must_fail git rebase --merge main side &&
+	git rebase --abort &&
+	git rebase --merge --ignore-whitespace main side &&
+	test_cmp expect file
+'
+
+test_expect_success '--ignore-whitespace is remembered when continuing' '
+	cat >expect <<-\EOF &&
+	line 1
+	new line 2
+	line 3
+	EOF
+	(
+		set_fake_editor &&
+		FAKE_LINES="break 1" git rebase -i --ignore-whitespace main side
+	) &&
+	git rebase --continue &&
+	test_cmp expect file
+'
+
+# This must be the last test in this file
+test_expect_success '$EDITOR and friends are unchanged' '
+	test_editor_unchanged
+'
+
+test_done

From ee9800cd95dcfb092c85625ca8e6c2a79d410453 Mon Sep 17 00:00:00 2001
From: Phillip Wood <phillip.wood@dunelm.org.uk>
Date: Wed, 27 May 2020 18:33:53 +0100
Subject: [PATCH 2/5] rebase -i: support --committer-date-is-author-date

As part of the on-going effort to retire the apply rebase backend teach
the merge backend how to handle --committer-date-is-author-date.

Original-patch-by: Rohit Ashiwal <rohit.ashiwal265@gmail.com>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-rebase.txt           | 10 +++--
 builtin/rebase.c                       | 16 ++++---
 sequencer.c                            | 59 +++++++++++++++++++++++++-
 sequencer.h                            |  1 +
 t/t3422-rebase-incompatible-options.sh |  1 -
 t/t3436-rebase-more-options.sh         | 56 ++++++++++++++++++++++++
 6 files changed, 133 insertions(+), 10 deletions(-)

diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index b003784f01..dfa70263e6 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -445,9 +445,13 @@ if the other side had no changes that conflicted.
 See also INCOMPATIBLE OPTIONS below.
 
 --committer-date-is-author-date::
+	Instead of using the current time as the committer date, use
+	the author date of the commit being rebased as the committer
+	date. This option implies --force-rebase.
+
 --ignore-date::
-	These flags are passed to 'git am' to easily change the dates
-	of the rebased commits (see linkgit:git-am[1]).
+	This flag is passed to 'git am' to change the author date
+	of each rebased commit (see linkgit:git-am[1]).
 +
 See also INCOMPATIBLE OPTIONS below.
 
@@ -585,7 +589,6 @@ INCOMPATIBLE OPTIONS
 The following options:
 
  * --apply
- * --committer-date-is-author-date
  * --ignore-date
  * --whitespace
  * -C
@@ -613,6 +616,7 @@ In addition, the following pairs of options are incompatible:
  * --preserve-merges and --rebase-merges
  * --preserve-merges and --empty=
  * --preserve-merges and --ignore-whitespace
+ * --preserve-merges and --committer-date-is-author-date
  * --keep-base and --onto
  * --keep-base and --root
 
diff --git a/builtin/rebase.c b/builtin/rebase.c
index 5d8e117276..357cd6acf3 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -89,6 +89,7 @@ struct rebase_options {
 	int ignore_whitespace;
 	char *gpg_sign_opt;
 	int autostash;
+	int committer_date_is_author_date;
 	char *cmd;
 	int allow_empty_message;
 	int rebase_merges, rebase_cousins;
@@ -126,6 +127,8 @@ static struct replay_opts get_replay_opts(const struct rebase_options *opts)
 	replay.quiet = !(opts->flags & REBASE_NO_QUIET);
 	replay.verbose = opts->flags & REBASE_VERBOSE;
 	replay.reschedule_failed_exec = opts->reschedule_failed_exec;
+	replay.committer_date_is_author_date =
+					opts->committer_date_is_author_date;
 	replay.gpg_sign = xstrdup_or_null(opts->gpg_sign_opt);
 	replay.strategy = opts->strategy;
 
@@ -1003,6 +1006,8 @@ static int run_am(struct rebase_options *opts)
 
 	if (opts->ignore_whitespace)
 		argv_array_push(&am.args, "--ignore-whitespace");
+	if (opts->committer_date_is_author_date)
+		argv_array_push(&opts->git_am_opts, "--committer-date-is-author-date");
 	if (opts->action && !strcmp("continue", opts->action)) {
 		argv_array_push(&am.args, "--resolved");
 		argv_array_pushf(&am.args, "--resolvemsg=%s", resolvemsg);
@@ -1507,9 +1512,9 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			PARSE_OPT_NOARG, NULL, REBASE_DIFFSTAT },
 		OPT_BOOL(0, "signoff", &options.signoff,
 			 N_("add a Signed-off-by: line to each commit")),
-		OPT_PASSTHRU_ARGV(0, "committer-date-is-author-date",
-				  &options.git_am_opts, NULL,
-				  N_("passed to 'git am'"), PARSE_OPT_NOARG),
+		OPT_BOOL(0, "committer-date-is-author-date",
+			 &options.committer_date_is_author_date,
+			 N_("make committer date match author date")),
 		OPT_PASSTHRU_ARGV(0, "ignore-date", &options.git_am_opts, NULL,
 				  N_("passed to 'git am'"), PARSE_OPT_NOARG),
 		OPT_PASSTHRU_ARGV('C', NULL, &options.git_am_opts, N_("n"),
@@ -1804,11 +1809,12 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	    options.autosquash) {
 		allow_preemptive_ff = 0;
 	}
+	if (options.committer_date_is_author_date)
+		options.flags |= REBASE_FORCE;
 
 	for (i = 0; i < options.git_am_opts.argc; i++) {
 		const char *option = options.git_am_opts.argv[i], *p;
-		if (!strcmp(option, "--committer-date-is-author-date") ||
-		    !strcmp(option, "--ignore-date") ||
+		if (!strcmp(option, "--ignore-date") ||
 		    !strcmp(option, "--whitespace=fix") ||
 		    !strcmp(option, "--whitespace=strip"))
 			allow_preemptive_ff = 0;
diff --git a/sequencer.c b/sequencer.c
index 6fd2674632..8826c6325b 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -149,6 +149,7 @@ static GIT_PATH_FUNC(rebase_path_refs_to_delete, "rebase-merge/refs-to-delete")
  * command-line.
  */
 static GIT_PATH_FUNC(rebase_path_gpg_sign_opt, "rebase-merge/gpg_sign_opt")
+static GIT_PATH_FUNC(rebase_path_cdate_is_adate, "rebase-merge/cdate_is_adate")
 static GIT_PATH_FUNC(rebase_path_orig_head, "rebase-merge/orig-head")
 static GIT_PATH_FUNC(rebase_path_verbose, "rebase-merge/verbose")
 static GIT_PATH_FUNC(rebase_path_quiet, "rebase-merge/quiet")
@@ -872,6 +873,22 @@ static char *get_author(const char *message)
 	return NULL;
 }
 
+static const char *author_date_from_env_array(const struct argv_array *env)
+{
+	int i;
+	const char *date;
+
+	for (i = 0; i < env->argc; i++)
+		if (skip_prefix(env->argv[i],
+				"GIT_AUTHOR_DATE=", &date))
+			return date;
+	/*
+	 * If GIT_AUTHOR_DATE is missing we should have already errored out when
+	 * reading the script
+	 */
+	BUG("GIT_AUTHOR_DATE missing from author script");
+}
+
 static const char staged_changes_advice[] =
 N_("you have staged changes in your working tree\n"
 "If these changes are meant to be squashed into the previous commit, run:\n"
@@ -938,6 +955,10 @@ static int run_git_commit(struct repository *r,
 			     gpg_opt, gpg_opt);
 	}
 
+	if (opts->committer_date_is_author_date)
+		argv_array_pushf(&cmd.env_array, "GIT_COMMITTER_DATE=%s",
+				 author_date_from_env_array(&cmd.env_array));
+
 	argv_array_push(&cmd.args, "commit");
 
 	if (!(flags & VERIFY_MSG))
@@ -1349,6 +1370,30 @@ static int try_to_commit(struct repository *r,
 		commit_list_insert(current_head, &parents);
 	}
 
+	if (opts->committer_date_is_author_date) {
+		int len = strlen(author);
+		struct ident_split ident;
+		struct strbuf date = STRBUF_INIT;
+
+		if (split_ident_line(&ident, author, len) < 0) {
+			res = error(_("malformed ident line '%s'"), author);
+			goto out;
+		}
+		if (!ident.date_begin) {
+			res = error(_("corrupted author without date information"));
+			goto out;
+		}
+
+		strbuf_addf(&date, "@%.*s %.*s",
+			    (int)(ident.date_end - ident.date_begin), ident.date_begin,
+			    (int)(ident.tz_end - ident.tz_begin), ident.tz_begin);
+		res = setenv("GIT_COMMITTER_DATE", date.buf, 1);
+		strbuf_release(&date);
+
+		if (res)
+			goto out;
+	}
+
 	if (write_index_as_tree(&tree, r->index, r->index_file, 0, NULL)) {
 		res = error(_("git write-tree failed to write a tree"));
 		goto out;
@@ -2532,6 +2577,11 @@ static int read_populate_opts(struct replay_opts *opts)
 			opts->signoff = 1;
 		}
 
+		if (file_exists(rebase_path_cdate_is_adate())) {
+			opts->allow_ff = 0;
+			opts->committer_date_is_author_date = 1;
+		}
+
 		if (file_exists(rebase_path_reschedule_failed_exec()))
 			opts->reschedule_failed_exec = 1;
 
@@ -2622,6 +2672,8 @@ int write_basic_state(struct replay_opts *opts, const char *head_name,
 		write_file(rebase_path_drop_redundant_commits(), "%s", "");
 	if (opts->keep_redundant_commits)
 		write_file(rebase_path_keep_redundant_commits(), "%s", "");
+	if (opts->committer_date_is_author_date)
+		write_file(rebase_path_cdate_is_adate(), "%s", "");
 	if (opts->reschedule_failed_exec)
 		write_file(rebase_path_reschedule_failed_exec(), "%s", "");
 
@@ -3542,6 +3594,10 @@ static int do_merge(struct repository *r,
 			goto leave_merge;
 		}
 
+		if (opts->committer_date_is_author_date)
+			argv_array_pushf(&cmd.env_array, "GIT_COMMITTER_DATE=%s",
+					 author_date_from_env_array(&cmd.env_array));
+
 		cmd.git_cmd = 1;
 		argv_array_push(&cmd.args, "merge");
 		argv_array_push(&cmd.args, "-s");
@@ -3819,7 +3875,8 @@ static int pick_commits(struct repository *r,
 	setenv(GIT_REFLOG_ACTION, action_name(opts), 0);
 	if (opts->allow_ff)
 		assert(!(opts->signoff || opts->no_commit ||
-				opts->record_origin || opts->edit));
+				opts->record_origin || opts->edit ||
+				opts->committer_date_is_author_date));
 	if (read_and_refresh_cache(r, opts))
 		return -1;
 
diff --git a/sequencer.h b/sequencer.h
index 0bee85093e..4ab94119ae 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -45,6 +45,7 @@ struct replay_opts {
 	int verbose;
 	int quiet;
 	int reschedule_failed_exec;
+	int committer_date_is_author_date;
 
 	int mainline;
 
diff --git a/t/t3422-rebase-incompatible-options.sh b/t/t3422-rebase-incompatible-options.sh
index 55ca46786d..c8234062c6 100755
--- a/t/t3422-rebase-incompatible-options.sh
+++ b/t/t3422-rebase-incompatible-options.sh
@@ -61,7 +61,6 @@ test_rebase_am_only () {
 }
 
 test_rebase_am_only --whitespace=fix
-test_rebase_am_only --committer-date-is-author-date
 test_rebase_am_only -C4
 
 test_expect_success REBASE_P '--preserve-merges incompatible with --signoff' '
diff --git a/t/t3436-rebase-more-options.sh b/t/t3436-rebase-more-options.sh
index fb5e747e86..7e68fb9753 100755
--- a/t/t3436-rebase-more-options.sh
+++ b/t/t3436-rebase-more-options.sh
@@ -9,6 +9,9 @@ test_description='tests to ensure compatibility between am and interactive backe
 
 . "$TEST_DIRECTORY"/lib-rebase.sh
 
+GIT_AUTHOR_DATE="1999-04-02T08:03:20+05:30"
+export GIT_AUTHOR_DATE
+
 # This is a special case in which both am and interactive backends
 # provide the same output. It was done intentionally because
 # both the backends fall short of optimal behaviour.
@@ -28,8 +31,13 @@ test_expect_success 'setup' '
 	EOF
 	git commit -am "update file" &&
 	git tag side &&
+	test_commit commit1 foo foo1 &&
+	test_commit commit2 foo foo2 &&
+	test_commit commit3 foo foo3 &&
 
 	git checkout --orphan master &&
+	git rm --cached foo &&
+	rm foo &&
 	sed -e "s/^|//" >file <<-\EOF &&
 	|line 1
 	|        line 2
@@ -78,6 +86,54 @@ test_expect_success '--ignore-whitespace is remembered when continuing' '
 	test_cmp expect file
 '
 
+test_expect_success '--committer-date-is-author-date works with apply backend' '
+	GIT_AUTHOR_DATE="@1234 +0300" git commit --amend --reset-author &&
+	git rebase --apply --committer-date-is-author-date HEAD^ &&
+	git log -1 --pretty=%ai >authortime &&
+	git log -1 --pretty=%ci >committertime &&
+	test_cmp authortime committertime
+'
+
+test_expect_success '--committer-date-is-author-date works with merge backend' '
+	GIT_AUTHOR_DATE="@1234 +0300" git commit --amend --reset-author &&
+	git rebase -m --committer-date-is-author-date HEAD^ &&
+	git log -1 --pretty=%ai >authortime &&
+	git log -1 --pretty=%ci >committertime &&
+	test_cmp authortime committertime
+'
+
+test_expect_success '--committer-date-is-author-date works with rebase -r' '
+	git checkout side &&
+	GIT_AUTHOR_DATE="@1234 +0300" git merge --no-ff commit3 &&
+	git rebase -r --root --committer-date-is-author-date &&
+	git log --pretty=%ai >authortime &&
+	git log --pretty=%ci >committertime &&
+	test_cmp authortime committertime
+'
+
+test_expect_success '--committer-date-is-author-date works when forking merge' '
+	git checkout side &&
+	GIT_AUTHOR_DATE="@1234 +0300" git merge --no-ff commit3 &&
+	git rebase -r --root --strategy=resolve --committer-date-is-author-date &&
+	git log --pretty=%ai >authortime &&
+	git log --pretty=%ci >committertime &&
+	test_cmp authortime committertime
+
+'
+
+test_expect_success '--committer-date-is-author-date works when committing conflict resolution' '
+	git checkout commit2 &&
+	GIT_AUTHOR_DATE="@1980 +0000" git commit --amend --only --reset-author &&
+	git log -1 --format=%at HEAD >expect &&
+	test_must_fail git rebase -m --committer-date-is-author-date \
+		--onto HEAD^^ HEAD^ &&
+	echo resolved > foo &&
+	git add foo &&
+	git rebase --continue &&
+	git log -1 --format=%ct HEAD >actual &&
+	test_cmp expect actual
+'
+
 # This must be the last test in this file
 test_expect_success '$EDITOR and friends are unchanged' '
 	test_editor_unchanged

From 9acb3a5de103977cdb55f786a01e387f09cde4aa Mon Sep 17 00:00:00 2001
From: Rohit Ashiwal <rohit.ashiwal265@gmail.com>
Date: Wed, 27 May 2020 18:33:54 +0100
Subject: [PATCH 3/5] sequencer: rename amend_author to author_to_free

The purpose of amend_author was to free() the malloc()'d string
obtained from get_author() when amending a commit. But we can
also use the variable to free() the author at our convenience.
Rename it to convey this meaning.

Signed-off-by: Rohit Ashiwal <rohit.ashiwal265@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sequencer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 8826c6325b..44e0b45e53 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1335,7 +1335,7 @@ static int try_to_commit(struct repository *r,
 	struct commit_extra_header *extra = NULL;
 	struct strbuf err = STRBUF_INIT;
 	struct strbuf commit_msg = STRBUF_INIT;
-	char *amend_author = NULL;
+	char *author_to_free = NULL;
 	const char *hook_commit = NULL;
 	enum commit_msg_cleanup_mode cleanup;
 	int res = 0;
@@ -1357,7 +1357,7 @@ static int try_to_commit(struct repository *r,
 			strbuf_addstr(msg, orig_message);
 			hook_commit = "HEAD";
 		}
-		author = amend_author = get_author(message);
+		author = author_to_free = get_author(message);
 		unuse_commit_buffer(current_head, message);
 		if (!author) {
 			res = error(_("unable to parse commit author"));
@@ -1473,7 +1473,7 @@ out:
 	free_commit_extra_headers(extra);
 	strbuf_release(&err);
 	strbuf_release(&commit_msg);
-	free(amend_author);
+	free(author_to_free);
 
 	return res;
 }

From 1a4437675ecca0a7366f9b880d3a9009f5d7a4d7 Mon Sep 17 00:00:00 2001
From: Phillip Wood <phillip.wood@dunelm.org.uk>
Date: Wed, 27 May 2020 18:33:55 +0100
Subject: [PATCH 4/5] rebase -i: support --ignore-date

As part of the on-going effort to retire the apply rebase backend
teach the merge backend how to handle --ignore-date. 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 <rohit.ashiwal265@gmail.com>
Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-rebase.txt   |  7 +++--
 builtin/rebase.c               | 13 +++++---
 sequencer.c                    | 50 +++++++++++++++++++++++++++--
 sequencer.h                    |  1 +
 t/t3436-rebase-more-options.sh | 57 ++++++++++++++++++++++++++++++++++
 5 files changed, 118 insertions(+), 10 deletions(-)

diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index dfa70263e6..e2717e20e6 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -450,8 +450,9 @@ See also INCOMPATIBLE OPTIONS below.
 	date. This option implies --force-rebase.
 
 --ignore-date::
-	This flag is passed to 'git am' to change the author date
-	of each rebased commit (see linkgit:git-am[1]).
+	Instead of using the author date of the original commit, use
+	the current time as the	author date of the rebased commit.  This
+	option implies `--force-rebase`.
 +
 See also INCOMPATIBLE OPTIONS below.
 
@@ -589,7 +590,6 @@ INCOMPATIBLE OPTIONS
 The following options:
 
  * --apply
- * --ignore-date
  * --whitespace
  * -C
 
@@ -617,6 +617,7 @@ In addition, the following pairs of options are incompatible:
  * --preserve-merges and --empty=
  * --preserve-merges and --ignore-whitespace
  * --preserve-merges and --committer-date-is-author-date
+ * --preserve-merges and --ignore-date
  * --keep-base and --onto
  * --keep-base and --root
 
diff --git a/builtin/rebase.c b/builtin/rebase.c
index 357cd6acf3..cf86240bc8 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -90,6 +90,7 @@ struct rebase_options {
 	char *gpg_sign_opt;
 	int autostash;
 	int committer_date_is_author_date;
+	int ignore_date;
 	char *cmd;
 	int allow_empty_message;
 	int rebase_merges, rebase_cousins;
@@ -129,6 +130,7 @@ static struct replay_opts get_replay_opts(const struct rebase_options *opts)
 	replay.reschedule_failed_exec = opts->reschedule_failed_exec;
 	replay.committer_date_is_author_date =
 					opts->committer_date_is_author_date;
+	replay.ignore_date = opts->ignore_date;
 	replay.gpg_sign = xstrdup_or_null(opts->gpg_sign_opt);
 	replay.strategy = opts->strategy;
 
@@ -1008,6 +1010,8 @@ static int run_am(struct rebase_options *opts)
 		argv_array_push(&am.args, "--ignore-whitespace");
 	if (opts->committer_date_is_author_date)
 		argv_array_push(&opts->git_am_opts, "--committer-date-is-author-date");
+	if (opts->ignore_date)
+		argv_array_push(&opts->git_am_opts, "--ignore-date");
 	if (opts->action && !strcmp("continue", opts->action)) {
 		argv_array_push(&am.args, "--resolved");
 		argv_array_pushf(&am.args, "--resolvemsg=%s", resolvemsg);
@@ -1515,8 +1519,8 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		OPT_BOOL(0, "committer-date-is-author-date",
 			 &options.committer_date_is_author_date,
 			 N_("make committer date match author date")),
-		OPT_PASSTHRU_ARGV(0, "ignore-date", &options.git_am_opts, NULL,
-				  N_("passed to 'git am'"), PARSE_OPT_NOARG),
+		OPT_BOOL(0, "ignore-date", &options.ignore_date,
+			 "ignore author date and use current date"),
 		OPT_PASSTHRU_ARGV('C', NULL, &options.git_am_opts, N_("n"),
 				  N_("passed to 'git apply'"), 0),
 		OPT_BOOL(0, "ignore-whitespace", &options.ignore_whitespace,
@@ -1809,13 +1813,12 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 	    options.autosquash) {
 		allow_preemptive_ff = 0;
 	}
-	if (options.committer_date_is_author_date)
+	if (options.committer_date_is_author_date || options.ignore_date)
 		options.flags |= REBASE_FORCE;
 
 	for (i = 0; i < options.git_am_opts.argc; i++) {
 		const char *option = options.git_am_opts.argv[i], *p;
-		if (!strcmp(option, "--ignore-date") ||
-		    !strcmp(option, "--whitespace=fix") ||
+		if (!strcmp(option, "--whitespace=fix") ||
 		    !strcmp(option, "--whitespace=strip"))
 			allow_preemptive_ff = 0;
 		else if (skip_prefix(option, "-C", &p)) {
diff --git a/sequencer.c b/sequencer.c
index 44e0b45e53..a21364c3be 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -150,6 +150,7 @@ static GIT_PATH_FUNC(rebase_path_refs_to_delete, "rebase-merge/refs-to-delete")
  */
 static GIT_PATH_FUNC(rebase_path_gpg_sign_opt, "rebase-merge/gpg_sign_opt")
 static GIT_PATH_FUNC(rebase_path_cdate_is_adate, "rebase-merge/cdate_is_adate")
+static GIT_PATH_FUNC(rebase_path_ignore_date, "rebase-merge/ignore_date")
 static GIT_PATH_FUNC(rebase_path_orig_head, "rebase-merge/orig-head")
 static GIT_PATH_FUNC(rebase_path_verbose, "rebase-merge/verbose")
 static GIT_PATH_FUNC(rebase_path_quiet, "rebase-merge/quiet")
@@ -889,6 +890,24 @@ static const char *author_date_from_env_array(const struct argv_array *env)
 	BUG("GIT_AUTHOR_DATE missing from author script");
 }
 
+/* Construct a free()able author string with current time as the author date */
+static char *ignore_author_date(const char *author)
+{
+	int len = strlen(author);
+	struct ident_split ident;
+	struct strbuf new_author = STRBUF_INIT;
+
+	if (split_ident_line(&ident, author, len) < 0) {
+		error(_("malformed ident line '%s'"), author);
+		return NULL;
+	}
+
+	len = ident.mail_end - ident.name_begin + 1;
+	strbuf_addf(&new_author, "%.*s ", len, ident.name_begin);
+	datestamp(&new_author);
+	return strbuf_detach(&new_author, NULL);
+}
+
 static const char staged_changes_advice[] =
 N_("you have staged changes in your working tree\n"
 "If these changes are meant to be squashed into the previous commit, run:\n"
@@ -957,7 +976,11 @@ static int run_git_commit(struct repository *r,
 
 	if (opts->committer_date_is_author_date)
 		argv_array_pushf(&cmd.env_array, "GIT_COMMITTER_DATE=%s",
+				 opts->ignore_date ?
+				 "" :
 				 author_date_from_env_array(&cmd.env_array));
+	if (opts->ignore_date)
+		argv_array_push(&cmd.env_array, "GIT_AUTHOR_DATE=");
 
 	argv_array_push(&cmd.args, "commit");
 
@@ -1387,7 +1410,8 @@ static int try_to_commit(struct repository *r,
 		strbuf_addf(&date, "@%.*s %.*s",
 			    (int)(ident.date_end - ident.date_begin), ident.date_begin,
 			    (int)(ident.tz_end - ident.tz_begin), ident.tz_begin);
-		res = setenv("GIT_COMMITTER_DATE", date.buf, 1);
+		res = setenv("GIT_COMMITTER_DATE",
+			     opts->ignore_date ? "" : date.buf, 1);
 		strbuf_release(&date);
 
 		if (res)
@@ -1453,6 +1477,16 @@ static int try_to_commit(struct repository *r,
 
 	reset_ident_date();
 
+	if (opts->ignore_date) {
+		author = ignore_author_date(author);
+		if (!author) {
+			res = -1;
+			goto out;
+		}
+		free(author_to_free);
+		author_to_free = (char *)author;
+	}
+
 	if (commit_tree_extended(msg->buf, msg->len, &tree, parents,
 				 oid, author, opts->gpg_sign, extra)) {
 		res = error(_("failed to write commit object"));
@@ -2582,6 +2616,11 @@ static int read_populate_opts(struct replay_opts *opts)
 			opts->committer_date_is_author_date = 1;
 		}
 
+		if (file_exists(rebase_path_ignore_date())) {
+			opts->allow_ff = 0;
+			opts->ignore_date = 1;
+		}
+
 		if (file_exists(rebase_path_reschedule_failed_exec()))
 			opts->reschedule_failed_exec = 1;
 
@@ -2674,6 +2713,8 @@ int write_basic_state(struct replay_opts *opts, const char *head_name,
 		write_file(rebase_path_keep_redundant_commits(), "%s", "");
 	if (opts->committer_date_is_author_date)
 		write_file(rebase_path_cdate_is_adate(), "%s", "");
+	if (opts->ignore_date)
+		write_file(rebase_path_ignore_date(), "%s", "");
 	if (opts->reschedule_failed_exec)
 		write_file(rebase_path_reschedule_failed_exec(), "%s", "");
 
@@ -3596,7 +3637,11 @@ static int do_merge(struct repository *r,
 
 		if (opts->committer_date_is_author_date)
 			argv_array_pushf(&cmd.env_array, "GIT_COMMITTER_DATE=%s",
+					 opts->ignore_date ?
+					 "" :
 					 author_date_from_env_array(&cmd.env_array));
+		if (opts->ignore_date)
+			argv_array_push(&cmd.env_array, "GIT_AUTHOR_DATE=");
 
 		cmd.git_cmd = 1;
 		argv_array_push(&cmd.args, "merge");
@@ -3876,7 +3921,8 @@ static int pick_commits(struct repository *r,
 	if (opts->allow_ff)
 		assert(!(opts->signoff || opts->no_commit ||
 				opts->record_origin || opts->edit ||
-				opts->committer_date_is_author_date));
+				opts->committer_date_is_author_date ||
+				opts->ignore_date));
 	if (read_and_refresh_cache(r, opts))
 		return -1;
 
diff --git a/sequencer.h b/sequencer.h
index 4ab94119ae..3587878e3b 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -46,6 +46,7 @@ struct replay_opts {
 	int quiet;
 	int reschedule_failed_exec;
 	int committer_date_is_author_date;
+	int ignore_date;
 
 	int mainline;
 
diff --git a/t/t3436-rebase-more-options.sh b/t/t3436-rebase-more-options.sh
index 7e68fb9753..a3f9d5b41a 100755
--- a/t/t3436-rebase-more-options.sh
+++ b/t/t3436-rebase-more-options.sh
@@ -134,6 +134,63 @@ test_expect_success '--committer-date-is-author-date works when committing confl
 	test_cmp expect actual
 '
 
+# Checking for +0000 in author time is enough since default
+# timezone is UTC, but the timezone used while committing
+# sets to +0530.
+test_expect_success '--ignore-date works with apply backend' '
+	git commit --amend --date="$GIT_AUTHOR_DATE" &&
+	git rebase --apply --ignore-date HEAD^ &&
+	git log -1 --pretty=%ai >authortime &&
+	grep "+0000" authortime
+'
+
+test_expect_success '--ignore-date works with merge backend' '
+	git commit --amend --date="$GIT_AUTHOR_DATE" &&
+	git rebase --ignore-date -m HEAD^ &&
+	git log -1 --pretty=%ai >authortime &&
+	grep "+0000" authortime
+'
+
+test_expect_success '--ignore-date works after conflict resolution' '
+	test_must_fail git rebase --ignore-date -m \
+		--onto commit2^^ commit2^ commit2 &&
+	echo resolved >foo &&
+	git add foo &&
+	git rebase --continue &&
+	git log -1 --pretty=%ai >authortime &&
+	grep +0000 authortime
+'
+
+test_expect_success '--ignore-date works with rebase -r' '
+	git checkout side &&
+	git merge --no-ff commit3 &&
+	git rebase -r --root --ignore-date &&
+	git log --pretty=%ai >authortime &&
+	! grep -v "+0000" authortime
+'
+
+test_expect_success '--ignore-date with --committer-date-is-author-date works' '
+	test_must_fail git rebase -m --committer-date-is-author-date \
+		--ignore-date --onto commit2^^ commit2^ commit3 &&
+	git checkout --theirs foo &&
+	git add foo &&
+	git rebase --continue &&
+	git log -2 --pretty=%ai >authortime &&
+	git log -2 --pretty=%ci >committertime &&
+	test_cmp authortime committertime &&
+	! grep -v "+0000" authortime
+'
+
+test_expect_success '--ignore-date --committer-date-is-author-date works when forking merge' '
+	GIT_SEQUENCE_EDITOR="echo \"merge -C $(git rev-parse HEAD) commit3\">" \
+		git rebase -i --strategy=resolve --ignore-date \
+		--committer-date-is-author-date side side &&
+	git log -1 --pretty=%ai >authortime &&
+	git log -1 --pretty=%ci >committertime &&
+	test_cmp authortime committertime &&
+	grep "+0000" authortime
+ '
+
 # This must be the last test in this file
 test_expect_success '$EDITOR and friends are unchanged' '
 	test_editor_unchanged

From 4fb554af49f8dc9ec5bacf14ad2d8fdd93a1cb5c Mon Sep 17 00:00:00 2001
From: Rohit Ashiwal <rohit.ashiwal265@gmail.com>
Date: Wed, 27 May 2020 18:33:56 +0100
Subject: [PATCH 5/5] rebase: add --reset-author-date

The previous commit introduced --ignore-date flag to rebase -i, but the
name is rather vague as it does not say whether the author date or the
committer date is ignored. Add an alias to convey the precise purpose.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Rohit Ashiwal <rohit.ashiwal265@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-rebase.txt   |  1 +
 builtin/rebase.c               |  6 ++++--
 t/t3436-rebase-more-options.sh | 34 ++++++++++++++++++++++------------
 3 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index e2717e20e6..a5f82913fb 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -450,6 +450,7 @@ See also INCOMPATIBLE OPTIONS below.
 	date. This option implies --force-rebase.
 
 --ignore-date::
+--reset-author-date::
 	Instead of using the author date of the original commit, use
 	the current time as the	author date of the rebased commit.  This
 	option implies `--force-rebase`.
diff --git a/builtin/rebase.c b/builtin/rebase.c
index cf86240bc8..911587690b 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -1519,8 +1519,10 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 		OPT_BOOL(0, "committer-date-is-author-date",
 			 &options.committer_date_is_author_date,
 			 N_("make committer date match author date")),
-		OPT_BOOL(0, "ignore-date", &options.ignore_date,
-			 "ignore author date and use current date"),
+		OPT_BOOL(0, "reset-author-date", &options.ignore_date,
+			 N_("ignore author date and use current date")),
+		OPT_HIDDEN_BOOL(0, "ignore-date", &options.ignore_date,
+				N_("synonym of --reset-author-date")),
 		OPT_PASSTHRU_ARGV('C', NULL, &options.git_am_opts, N_("n"),
 				  N_("passed to 'git apply'"), 0),
 		OPT_BOOL(0, "ignore-whitespace", &options.ignore_whitespace,
diff --git a/t/t3436-rebase-more-options.sh b/t/t3436-rebase-more-options.sh
index a3f9d5b41a..ecfd68397f 100755
--- a/t/t3436-rebase-more-options.sh
+++ b/t/t3436-rebase-more-options.sh
@@ -137,22 +137,22 @@ test_expect_success '--committer-date-is-author-date works when committing confl
 # Checking for +0000 in author time is enough since default
 # timezone is UTC, but the timezone used while committing
 # sets to +0530.
-test_expect_success '--ignore-date works with apply backend' '
+test_expect_success '--reset-author-date works with apply backend' '
 	git commit --amend --date="$GIT_AUTHOR_DATE" &&
-	git rebase --apply --ignore-date HEAD^ &&
+	git rebase --apply --reset-author-date HEAD^ &&
 	git log -1 --pretty=%ai >authortime &&
 	grep "+0000" authortime
 '
 
-test_expect_success '--ignore-date works with merge backend' '
+test_expect_success '--reset-author-date works with merge backend' '
 	git commit --amend --date="$GIT_AUTHOR_DATE" &&
-	git rebase --ignore-date -m HEAD^ &&
+	git rebase --reset-author-date -m HEAD^ &&
 	git log -1 --pretty=%ai >authortime &&
 	grep "+0000" authortime
 '
 
-test_expect_success '--ignore-date works after conflict resolution' '
-	test_must_fail git rebase --ignore-date -m \
+test_expect_success '--reset-author-date works after conflict resolution' '
+	test_must_fail git rebase --reset-author-date -m \
 		--onto commit2^^ commit2^ commit2 &&
 	echo resolved >foo &&
 	git add foo &&
@@ -161,17 +161,17 @@ test_expect_success '--ignore-date works after conflict resolution' '
 	grep +0000 authortime
 '
 
-test_expect_success '--ignore-date works with rebase -r' '
+test_expect_success '--reset-author-date works with rebase -r' '
 	git checkout side &&
 	git merge --no-ff commit3 &&
-	git rebase -r --root --ignore-date &&
+	git rebase -r --root --reset-author-date &&
 	git log --pretty=%ai >authortime &&
 	! grep -v "+0000" authortime
 '
 
-test_expect_success '--ignore-date with --committer-date-is-author-date works' '
+test_expect_success '--reset-author-date with --committer-date-is-author-date works' '
 	test_must_fail git rebase -m --committer-date-is-author-date \
-		--ignore-date --onto commit2^^ commit2^ commit3 &&
+		--reset-author-date --onto commit2^^ commit2^ commit3 &&
 	git checkout --theirs foo &&
 	git add foo &&
 	git rebase --continue &&
@@ -181,9 +181,9 @@ test_expect_success '--ignore-date with --committer-date-is-author-date works' '
 	! grep -v "+0000" authortime
 '
 
-test_expect_success '--ignore-date --committer-date-is-author-date works when forking merge' '
+test_expect_success '--reset-author-date --committer-date-is-author-date works when forking merge' '
 	GIT_SEQUENCE_EDITOR="echo \"merge -C $(git rev-parse HEAD) commit3\">" \
-		git rebase -i --strategy=resolve --ignore-date \
+		git rebase -i --strategy=resolve --reset-author-date \
 		--committer-date-is-author-date side side &&
 	git log -1 --pretty=%ai >authortime &&
 	git log -1 --pretty=%ci >committertime &&
@@ -191,6 +191,16 @@ test_expect_success '--ignore-date --committer-date-is-author-date works when fo
 	grep "+0000" authortime
  '
 
+test_expect_success '--ignore-date is an alias for --reset-author-date' '
+	git commit --amend --date="$GIT_AUTHOR_DATE" &&
+	git rebase --apply --ignore-date HEAD^ &&
+	git commit --allow-empty -m empty --date="$GIT_AUTHOR_DATE" &&
+	git rebase -m --ignore-date HEAD^ &&
+	git log -2 --pretty=%ai >authortime &&
+	grep "+0000" authortime >output &&
+	test_line_count = 2 output
+'
+
 # This must be the last test in this file
 test_expect_success '$EDITOR and friends are unchanged' '
 	test_editor_unchanged