Merge branch 'dl/rebase-i-keep-base'

"git rebase --keep-base <upstream>" tries to find the original base
of the topic being rebased and rebase on top of that same base,
which is useful when running the "git rebase -i" (and its limited
variant "git rebase -x").

The command also has learned to fast-forward in more cases where it
can instead of replaying to recreate identical commits.

* dl/rebase-i-keep-base:
  rebase: teach rebase --keep-base
  rebase tests: test linear branch topology
  rebase: fast-forward --fork-point in more cases
  rebase: fast-forward --onto in more cases
  rebase: refactor can_fast_forward into goto tower
  t3432: test for --no-ff's interaction with fast-forward
  t3432: distinguish "noop-same" v.s. "work-same" in "same head" tests
  t3432: test rebase fast-forward behavior
  t3431: add rebase --fork-point tests

6 files changed, 270 insertions, 2 deletions

diff --git a/t/t3400-rebase.sh b/t/t3400-rebase.sh
index 23469cc789..ab18ac5f28 100755
--- a/t/t3400-rebase.sh
+++ b/t/t3400-rebase.sh
@@ -295,7 +295,7 @@ test_expect_success 'rebase --am and --show-current-patch' '
 		echo two >>init.t &&
 		git commit -a -m two &&
 		git tag two &&
-		test_must_fail git rebase --onto init HEAD^ &&
+		test_must_fail git rebase -f --onto init HEAD^ &&
 		GIT_TRACE=1 git rebase --show-current-patch >/dev/null 2>stderr &&
 		grep "show.*$(git rev-parse two)" stderr
 	)
diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
index 04affcc38a..29a35840ed 100755
--- a/t/t3404-rebase-interactive.sh
+++ b/t/t3404-rebase-interactive.sh
@@ -1056,7 +1056,7 @@ test_expect_success C_LOCALE_OUTPUT 'rebase --edit-todo does not work on non-int
 	git reset --hard &&
 	git checkout conflict-branch &&
 	set_fake_editor &&
-	test_must_fail git rebase --onto HEAD~2 HEAD~ &&
+	test_must_fail git rebase -f --onto HEAD~2 HEAD~ &&
 	test_must_fail git rebase --edit-todo &&
 	git rebase --abort
 '
diff --git a/t/t3416-rebase-onto-threedots.sh b/t/t3416-rebase-onto-threedots.sh
index ddf2f64853..9c2548423b 100755
--- a/t/t3416-rebase-onto-threedots.sh
+++ b/t/t3416-rebase-onto-threedots.sh
@@ -99,7 +99,64 @@ test_expect_success 'rebase -i --onto master...side' '
 	git checkout side &&
 	git reset --hard K &&
 
+	set_fake_editor &&
 	test_must_fail git rebase -i --onto master...side J
 '
 
+test_expect_success 'rebase --keep-base --onto incompatible' '
+	test_must_fail git rebase --keep-base --onto master...
+'
+
+test_expect_success 'rebase --keep-base --root incompatible' '
+	test_must_fail git rebase --keep-base --root
+'
+
+test_expect_success 'rebase --keep-base master from topic' '
+	git reset --hard &&
+	git checkout topic &&
+	git reset --hard G &&
+
+	git rebase --keep-base master &&
+	git rev-parse C >base.expect &&
+	git merge-base master HEAD >base.actual &&
+	test_cmp base.expect base.actual &&
+
+	git rev-parse HEAD~2 >actual &&
+	git rev-parse C^0 >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase --keep-base master from side' '
+	git reset --hard &&
+	git checkout side &&
+	git reset --hard K &&
+
+	test_must_fail git rebase --keep-base master
+'
+
+test_expect_success 'rebase -i --keep-base master from topic' '
+	git reset --hard &&
+	git checkout topic &&
+	git reset --hard G &&
+
+	set_fake_editor &&
+	EXPECT_COUNT=2 git rebase -i --keep-base master &&
+	git rev-parse C >base.expect &&
+	git merge-base master HEAD >base.actual &&
+	test_cmp base.expect base.actual &&
+
+	git rev-parse HEAD~2 >actual &&
+	git rev-parse C^0 >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'rebase -i --keep-base master from side' '
+	git reset --hard &&
+	git checkout side &&
+	git reset --hard K &&
+
+	set_fake_editor &&
+	test_must_fail git rebase -i --keep-base master
+'
+
 test_done
diff --git a/t/t3421-rebase-topology-linear.sh b/t/t3421-rebase-topology-linear.sh
index 7274dca40b..b847064f91 100755
--- a/t/t3421-rebase-topology-linear.sh
+++ b/t/t3421-rebase-topology-linear.sh
@@ -31,6 +31,16 @@ test_run_rebase success -m
 test_run_rebase success -i
 test_have_prereq !REBASE_P || test_run_rebase success -p
 
+test_expect_success 'setup branches and remote tracking' '
+	git tag -l >tags &&
+	for tag in $(cat tags)
+	do
+		git branch branch-$tag $tag || return 1
+	done &&
+	git remote add origin "file://$PWD" &&
+	git fetch origin
+'
+
 test_run_rebase () {
 	result=$1
 	shift
@@ -57,6 +67,7 @@ test_run_rebase () {
 	"
 }
 test_run_rebase success ''
+test_run_rebase success --fork-point
 test_run_rebase success -m
 test_run_rebase success -i
 test_have_prereq !REBASE_P || test_run_rebase failure -p
@@ -64,6 +75,23 @@ test_have_prereq !REBASE_P || test_run_rebase failure -p
 test_run_rebase () {
 	result=$1
 	shift
+	test_expect_$result "rebase $* -f rewrites even if remote upstream is an ancestor" "
+		reset_rebase &&
+		git rebase $* -f branch-b branch-e &&
+		! test_cmp_rev branch-e origin/branch-e &&
+		test_cmp_rev branch-b HEAD~2 &&
+		test_linear_range 'd e' branch-b..
+	"
+}
+test_run_rebase success ''
+test_run_rebase success --fork-point
+test_run_rebase success -m
+test_run_rebase success -i
+test_have_prereq !REBASE_P || test_run_rebase success -p
+
+test_run_rebase () {
+	result=$1
+	shift
 	test_expect_$result "rebase $* fast-forwards from ancestor of upstream" "
 		reset_rebase &&
 		git rebase $* e b &&
@@ -71,6 +99,7 @@ test_run_rebase () {
 	"
 }
 test_run_rebase success ''
+test_run_rebase success --fork-point
 test_run_rebase success -m
 test_run_rebase success -i
 test_have_prereq !REBASE_P || test_run_rebase success -p
diff --git a/t/t3431-rebase-fork-point.sh b/t/t3431-rebase-fork-point.sh
new file mode 100755
index 0000000000..78851b9a2a
--- /dev/null
+++ b/t/t3431-rebase-fork-point.sh
@@ -0,0 +1,57 @@
+#!/bin/sh
+#
+# Copyright (c) 2019 Denton Liu
+#
+
+test_description='git rebase --fork-point test'
+
+. ./test-lib.sh
+
+# A---B---D---E    (master)
+#      \
+#       C*---F---G (side)
+#
+# C was formerly part of master but master was rewound to remove C
+#
+test_expect_success setup '
+	test_commit A &&
+	test_commit B &&
+	test_commit C &&
+	git branch -t side &&
+	git reset --hard HEAD^ &&
+	test_commit D &&
+	test_commit E &&
+	git checkout side &&
+	test_commit F &&
+	test_commit G
+'
+
+test_rebase () {
+	expected="$1" &&
+	shift &&
+	test_expect_success "git rebase $*" "
+		git checkout master &&
+		git reset --hard E &&
+		git checkout side &&
+		git reset --hard G &&
+		git rebase $* &&
+		test_write_lines $expected >expect &&
+		git log --pretty=%s >actual &&
+		test_cmp expect actual
+	"
+}
+
+test_rebase 'G F E D B A'
+test_rebase 'G F D B A' --onto D
+test_rebase 'G F B A' --keep-base
+test_rebase 'G F C E D B A' --no-fork-point
+test_rebase 'G F C D B A' --no-fork-point --onto D
+test_rebase 'G F C B A' --no-fork-point --keep-base
+test_rebase 'G F E D B A' --fork-point refs/heads/master
+test_rebase 'G F D B A' --fork-point --onto D refs/heads/master
+test_rebase 'G F B A' --fork-point --keep-base refs/heads/master
+test_rebase 'G F C E D B A' refs/heads/master
+test_rebase 'G F C D B A' --onto D refs/heads/master
+test_rebase 'G F C B A' --keep-base refs/heads/master
+
+test_done
diff --git a/t/t3432-rebase-fast-forward.sh b/t/t3432-rebase-fast-forward.sh
new file mode 100755
index 0000000000..034ffc7e76
--- /dev/null
+++ b/t/t3432-rebase-fast-forward.sh
@@ -0,0 +1,125 @@
+#!/bin/sh
+#
+# Copyright (c) 2019 Denton Liu
+#
+
+test_description='ensure rebase fast-forwards commits when possible'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	test_commit A &&
+	test_commit B &&
+	test_commit C &&
+	test_commit D &&
+	git checkout -t -b side
+'
+
+test_rebase_same_head () {
+	status_n="$1" &&
+	shift &&
+	what_n="$1" &&
+	shift &&
+	cmp_n="$1" &&
+	shift &&
+	status_f="$1" &&
+	shift &&
+	what_f="$1" &&
+	shift &&
+	cmp_f="$1" &&
+	shift &&
+	test_rebase_same_head_ $status_n $what_n $cmp_n "" "$*" &&
+	test_rebase_same_head_ $status_f $what_f $cmp_f " --no-ff" "$*"
+}
+
+test_rebase_same_head_ () {
+	status="$1" &&
+	shift &&
+	what="$1" &&
+	shift &&
+	cmp="$1" &&
+	shift &&
+	flag="$1"
+	shift &&
+	test_expect_$status "git rebase$flag $* with $changes is $what with $cmp HEAD" "
+		oldhead=\$(git rev-parse HEAD) &&
+		test_when_finished 'git reset --hard \$oldhead' &&
+		git rebase$flag $* >stdout &&
+		if test $what = work
+		then
+			# Must check this case first, for 'is up to
+			# date, rebase forced[...]rewinding head' cases
+			test_i18ngrep 'rewinding head' stdout
+		elif test $what = noop
+		then
+			test_i18ngrep 'is up to date' stdout &&
+			test_i18ngrep ! 'rebase forced' stdout
+		elif test $what = noop-force
+		then
+			test_i18ngrep 'is up to date, rebase forced' stdout
+		fi &&
+		newhead=\$(git rev-parse HEAD) &&
+		if test $cmp = same
+		then
+			test_cmp_rev \$oldhead \$newhead
+		elif test $cmp = diff
+		then
+			! test_cmp_rev \$oldhead \$newhead
+		fi
+	"
+}
+
+changes='no changes'
+test_rebase_same_head success noop same success work same
+test_rebase_same_head success noop same success noop-force same master
+test_rebase_same_head success noop same success noop-force diff --onto B B
+test_rebase_same_head success noop same success noop-force diff --onto B... B
+test_rebase_same_head success noop same success noop-force same --onto master... master
+test_rebase_same_head success noop same success noop-force same --keep-base master
+test_rebase_same_head success noop same success noop-force same --keep-base
+test_rebase_same_head success noop same success noop-force same --no-fork-point
+test_rebase_same_head success noop same success noop-force same --keep-base --no-fork-point
+test_rebase_same_head success noop same success work same --fork-point master
+test_rebase_same_head success noop same success work diff --fork-point --onto B B
+test_rebase_same_head success noop same success work diff --fork-point --onto B... B
+test_rebase_same_head success noop same success work same --fork-point --onto master... master
+test_rebase_same_head success noop same success work same --keep-base --keep-base master
+
+test_expect_success 'add work same to side' '
+	test_commit E
+'
+
+changes='our changes'
+test_rebase_same_head success noop same success work same
+test_rebase_same_head success noop same success noop-force same master
+test_rebase_same_head success noop same success noop-force diff --onto B B
+test_rebase_same_head success noop same success noop-force diff --onto B... B
+test_rebase_same_head success noop same success noop-force same --onto master... master
+test_rebase_same_head success noop same success noop-force same --keep-base master
+test_rebase_same_head success noop same success noop-force same --keep-base
+test_rebase_same_head success noop same success noop-force same --no-fork-point
+test_rebase_same_head success noop same success noop-force same --keep-base --no-fork-point
+test_rebase_same_head success noop same success work same --fork-point master
+test_rebase_same_head success noop same success work diff --fork-point --onto B B
+test_rebase_same_head success noop same success work diff --fork-point --onto B... B
+test_rebase_same_head success noop same success work same --fork-point --onto master... master
+test_rebase_same_head success noop same success work same --fork-point --keep-base master
+
+test_expect_success 'add work same to upstream' '
+	git checkout master &&
+	test_commit F &&
+	git checkout side
+'
+
+changes='our and their changes'
+test_rebase_same_head success noop same success noop-force diff --onto B B
+test_rebase_same_head success noop same success noop-force diff --onto B... B
+test_rebase_same_head success noop same success work diff --onto master... master
+test_rebase_same_head success noop same success work diff --keep-base master
+test_rebase_same_head success noop same success work diff --keep-base
+test_rebase_same_head failure work same success work diff --fork-point --onto B B
+test_rebase_same_head failure work same success work diff --fork-point --onto B... B
+test_rebase_same_head success noop same success work diff --fork-point --onto master... master
+test_rebase_same_head success noop same success work diff --fork-point --keep-base master
+
+test_done