merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 617 insertions, 272 deletions

diff --git a/third_party/git/t/t3404-rebase-interactive.sh b/third_party/git/t/t3404-rebase-interactive.sh
index 461dd539ff..07a1617351 100755
--- a/third_party/git/t/t3404-rebase-interactive.sh
+++ b/third_party/git/t/t3404-rebase-interactive.sh
@@ -29,9 +29,6 @@ Initial setup:
 
 . "$TEST_DIRECTORY"/lib-rebase.sh
 
-# WARNING: Modifications to the initial repository can change the SHA ID used
-# in the expect2 file for the 'stop on conflicting pick' test.
-
 test_expect_success 'setup' '
 	test_commit A file1 &&
 	test_commit B file1 &&
@@ -75,12 +72,16 @@ test_expect_success 'rebase --keep-empty' '
 	test_line_count = 6 actual
 '
 
-test_expect_success 'rebase -i with empty HEAD' '
+test_expect_success 'rebase -i with empty todo list' '
 	cat >expect <<-\EOF &&
 	error: nothing to do
 	EOF
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 exec_true" git rebase -i HEAD^ >actual 2>&1 &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="#" \
+			git rebase -i HEAD^ >output 2>&1
+	) &&
+	tail -n 1 output >actual &&  # Ignore output about changing todo list
 	test_i18ncmp expect actual
 '
 
@@ -139,8 +140,11 @@ test_expect_success 'rebase -i sets work tree properly' '
 
 test_expect_success 'rebase -i with the exec command checks tree cleanness' '
 	git checkout master &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="exec_echo_foo_>file1 1" git rebase -i HEAD^ &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="exec_echo_foo_>file1 1" \
+			git rebase -i HEAD^
+	) &&
 	test_cmp_rev master^ HEAD &&
 	git reset --hard &&
 	git rebase --continue
@@ -155,8 +159,6 @@ test_expect_success 'rebase -x with empty command fails' '
 	test_i18ncmp expected actual
 '
 
-LF='
-'
 test_expect_success 'rebase -x with newline in command fails' '
 	test_when_finished "git rebase --abort ||:" &&
 	test_must_fail env git rebase -x "a${LF}b" @ 2>actual &&
@@ -168,9 +170,11 @@ test_expect_success 'rebase -x with newline in command fails' '
 test_expect_success 'rebase -i with exec of inexistent command' '
 	git checkout master &&
 	test_when_finished "git rebase --abort" &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="exec_this-command-does-not-exist 1" \
-	git rebase -i HEAD^ >actual 2>&1 &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="exec_this-command-does-not-exist 1" \
+			git rebase -i HEAD^ >actual 2>&1
+	) &&
 	! grep "Maybe git-rebase is broken" actual
 '
 
@@ -181,80 +185,80 @@ test_expect_success 'implicit interactive rebase does not invoke sequence editor
 
 test_expect_success 'no changes are a nop' '
 	git checkout branch2 &&
-	set_fake_editor &&
 	git rebase -i F &&
 	test "$(git symbolic-ref -q HEAD)" = "refs/heads/branch2" &&
-	test $(git rev-parse I) = $(git rev-parse HEAD)
+	test_cmp_rev I HEAD
 '
 
 test_expect_success 'test the [branch] option' '
 	git checkout -b dead-end &&
 	git rm file6 &&
 	git commit -m "stop here" &&
-	set_fake_editor &&
 	git rebase -i F branch2 &&
 	test "$(git symbolic-ref -q HEAD)" = "refs/heads/branch2" &&
-	test $(git rev-parse I) = $(git rev-parse branch2) &&
-	test $(git rev-parse I) = $(git rev-parse HEAD)
+	test_cmp_rev I branch2 &&
+	test_cmp_rev I HEAD
 '
 
 test_expect_success 'test --onto <branch>' '
 	git checkout -b test-onto branch2 &&
-	set_fake_editor &&
 	git rebase -i --onto branch1 F &&
 	test "$(git symbolic-ref -q HEAD)" = "refs/heads/test-onto" &&
-	test $(git rev-parse HEAD^) = $(git rev-parse branch1) &&
-	test $(git rev-parse I) = $(git rev-parse branch2)
+	test_cmp_rev HEAD^ branch1 &&
+	test_cmp_rev I branch2
 '
 
 test_expect_success 'rebase on top of a non-conflicting commit' '
 	git checkout branch1 &&
 	git tag original-branch1 &&
-	set_fake_editor &&
 	git rebase -i branch2 &&
 	test file6 = $(git diff --name-only original-branch1) &&
 	test "$(git symbolic-ref -q HEAD)" = "refs/heads/branch1" &&
-	test $(git rev-parse I) = $(git rev-parse branch2) &&
-	test $(git rev-parse I) = $(git rev-parse HEAD~2)
+	test_cmp_rev I branch2 &&
+	test_cmp_rev I HEAD~2
 '
 
 test_expect_success 'reflog for the branch shows state before rebase' '
-	test $(git rev-parse branch1@{1}) = $(git rev-parse original-branch1)
+	test_cmp_rev branch1@{1} original-branch1
 '
 
 test_expect_success 'reflog for the branch shows correct finish message' '
-	printf "rebase -i (finish): refs/heads/branch1 onto %s\n" \
+	printf "rebase (finish): refs/heads/branch1 onto %s\n" \
 		"$(git rev-parse branch2)" >expected &&
 	git log -g --pretty=%gs -1 refs/heads/branch1 >actual &&
 	test_cmp expected actual
 '
 
 test_expect_success 'exchange two commits' '
-	set_fake_editor &&
-	FAKE_LINES="2 1" git rebase -i HEAD~2 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="2 1" git rebase -i HEAD~2
+	) &&
 	test H = $(git cat-file commit HEAD^ | sed -ne \$p) &&
-	test G = $(git cat-file commit HEAD | sed -ne \$p)
+	test G = $(git cat-file commit HEAD | sed -ne \$p) &&
+	blob1=$(git rev-parse --short HEAD^:file1) &&
+	blob2=$(git rev-parse --short HEAD:file1) &&
+	commit=$(git rev-parse --short HEAD)
 '
 
 test_expect_success 'stop on conflicting pick' '
-	cat >expect <<-\EOF &&
+	cat >expect <<-EOF &&
 	diff --git a/file1 b/file1
-	index f70f10e..fd79235 100644
+	index $blob1..$blob2 100644
 	--- a/file1
 	+++ b/file1
 	@@ -1 +1 @@
 	-A
 	+G
 	EOF
-	cat >expect2 <<-\EOF &&
+	cat >expect2 <<-EOF &&
 	<<<<<<< HEAD
 	D
 	=======
 	G
-	>>>>>>> 5d18e54... G
+	>>>>>>> $commit (G)
 	EOF
 	git tag new-branch1 &&
-	set_fake_editor &&
 	test_must_fail git rebase -i master &&
 	test "$(git rev-parse HEAD~3)" = "$(git rev-parse master)" &&
 	test_cmp expect .git/rebase-merge/patch &&
@@ -275,7 +279,7 @@ test_expect_success 'show conflicted patch' '
 
 test_expect_success 'abort' '
 	git rebase --abort &&
-	test $(git rev-parse new-branch1) = $(git rev-parse HEAD) &&
+	test_cmp_rev new-branch1 HEAD &&
 	test "$(git symbolic-ref -q HEAD)" = "refs/heads/branch1" &&
 	test_path_is_missing .git/rebase-merge
 '
@@ -283,7 +287,6 @@ test_expect_success 'abort' '
 test_expect_success 'abort with error when new base cannot be checked out' '
 	git rm --cached file1 &&
 	git commit -m "remove file in base" &&
-	set_fake_editor &&
 	test_must_fail git rebase -i master > output 2>&1 &&
 	test_i18ngrep "The following untracked working tree files would be overwritten by checkout:" \
 		output &&
@@ -298,7 +301,6 @@ test_expect_success 'retain authorship' '
 	test_tick &&
 	GIT_AUTHOR_NAME="Twerp Snog" git commit -m "different author" &&
 	git tag twerp &&
-	set_fake_editor &&
 	git rebase -i --onto master HEAD^ &&
 	git show HEAD | grep "^Author: Twerp Snog"
 '
@@ -316,12 +318,11 @@ test_expect_success 'retain authorship w/ conflicts' '
 	test_commit b conflict b conflict-b &&
 	GIT_AUTHOR_NAME=$oGIT_AUTHOR_NAME &&
 
-	set_fake_editor &&
 	test_must_fail git rebase -i conflict-a &&
 	echo resolved >conflict &&
 	git add conflict &&
 	git rebase --continue &&
-	test $(git rev-parse conflict-a^0) = $(git rev-parse HEAD^) &&
+	test_cmp_rev conflict-a^0 HEAD^ &&
 	git show >out &&
 	grep AttributeMe out
 '
@@ -332,11 +333,13 @@ test_expect_success 'squash' '
 	test_tick &&
 	GIT_AUTHOR_NAME="Nitfol" git commit -m "nitfol" file7 &&
 	echo "******************************" &&
-	set_fake_editor &&
-	FAKE_LINES="1 squash 2" EXPECT_HEADER_COUNT=2 \
-		git rebase -i --onto master HEAD~2 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 squash 2" EXPECT_HEADER_COUNT=2 \
+			git rebase -i --onto master HEAD~2
+	) &&
 	test B = $(cat file7) &&
-	test $(git rev-parse HEAD^) = $(git rev-parse master)
+	test_cmp_rev HEAD^ master
 '
 
 test_expect_success 'retain authorship when squashing' '
@@ -345,7 +348,6 @@ test_expect_success 'retain authorship when squashing' '
 
 test_expect_success REBASE_P '-p handles "no changes" gracefully' '
 	HEAD=$(git rev-parse HEAD) &&
-	set_fake_editor &&
 	git rebase -i -p HEAD^ &&
 	git update-index --refresh &&
 	git diff-files --quiet &&
@@ -355,8 +357,10 @@ test_expect_success REBASE_P '-p handles "no changes" gracefully' '
 
 test_expect_failure REBASE_P 'exchange two commits with -p' '
 	git checkout H &&
-	set_fake_editor &&
-	FAKE_LINES="2 1" git rebase -i -p HEAD~2 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="2 1" git rebase -i -p HEAD~2
+	) &&
 	test H = $(git cat-file commit HEAD^ | sed -ne \$p) &&
 	test G = $(git cat-file commit HEAD | sed -ne \$p)
 '
@@ -390,14 +394,13 @@ test_expect_success REBASE_P 'preserve merges with -p' '
 	git commit -m M file1 &&
 	git checkout -b to-be-rebased &&
 	test_tick &&
-	set_fake_editor &&
 	git rebase -i -p --onto branch1 master &&
 	git update-index --refresh &&
 	git diff-files --quiet &&
 	git diff-index --quiet --cached HEAD -- &&
-	test $(git rev-parse HEAD~6) = $(git rev-parse branch1) &&
-	test $(git rev-parse HEAD~4^2) = $(git rev-parse to-be-preserved) &&
-	test $(git rev-parse HEAD^^2^) = $(git rev-parse HEAD^^^) &&
+	test_cmp_rev HEAD~6 branch1 &&
+	test_cmp_rev HEAD~4^2 to-be-preserved &&
+	test_cmp_rev HEAD^^2^ HEAD^^^ &&
 	test $(git show HEAD~5:file1) = B &&
 	test $(git show HEAD~3:file1) = C &&
 	test $(git show HEAD:file1) = E &&
@@ -405,8 +408,10 @@ test_expect_success REBASE_P 'preserve merges with -p' '
 '
 
 test_expect_success REBASE_P 'edit ancestor with -p' '
-	set_fake_editor &&
-	FAKE_LINES="1 2 edit 3 4" git rebase -i -p HEAD~3 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 2 edit 3 4" git rebase -i -p HEAD~3
+	) &&
 	echo 2 > unrelated-file &&
 	test_tick &&
 	git commit -m L2-modified --amend unrelated-file &&
@@ -420,19 +425,20 @@ test_expect_success REBASE_P 'edit ancestor with -p' '
 test_expect_success '--continue tries to commit' '
 	git reset --hard D &&
 	test_tick &&
-	set_fake_editor &&
-	test_must_fail git rebase -i --onto new-branch1 HEAD^ &&
-	echo resolved > file1 &&
-	git add file1 &&
-	FAKE_COMMIT_MESSAGE="chouette!" git rebase --continue &&
-	test $(git rev-parse HEAD^) = $(git rev-parse new-branch1) &&
+	(
+		set_fake_editor &&
+		test_must_fail git rebase -i --onto new-branch1 HEAD^ &&
+		echo resolved > file1 &&
+		git add file1 &&
+		FAKE_COMMIT_MESSAGE="chouette!" git rebase --continue
+	) &&
+	test_cmp_rev HEAD^ new-branch1 &&
 	git show HEAD | grep chouette
 '
 
 test_expect_success 'verbose flag is heeded, even after --continue' '
 	git reset --hard master@{1} &&
 	test_tick &&
-	set_fake_editor &&
 	test_must_fail git rebase -v -i --onto new-branch1 HEAD^ &&
 	echo resolved > file1 &&
 	git add file1 &&
@@ -442,10 +448,13 @@ test_expect_success 'verbose flag is heeded, even after --continue' '
 
 test_expect_success C_LOCALE_OUTPUT 'multi-squash only fires up editor once' '
 	base=$(git rev-parse HEAD~4) &&
-	set_fake_editor &&
-	FAKE_COMMIT_AMEND="ONCE" FAKE_LINES="1 squash 2 squash 3 squash 4" \
-		EXPECT_HEADER_COUNT=4 \
-		git rebase -i $base &&
+	(
+		set_fake_editor &&
+		FAKE_COMMIT_AMEND="ONCE" \
+			FAKE_LINES="1 squash 2 squash 3 squash 4" \
+			EXPECT_HEADER_COUNT=4 \
+			git rebase -i $base
+	) &&
 	test $base = $(git rev-parse HEAD^) &&
 	test 1 = $(git show | grep ONCE | wc -l)
 '
@@ -453,9 +462,12 @@ test_expect_success C_LOCALE_OUTPUT 'multi-squash only fires up editor once' '
 test_expect_success C_LOCALE_OUTPUT 'multi-fixup does not fire up editor' '
 	git checkout -b multi-fixup E &&
 	base=$(git rev-parse HEAD~4) &&
-	set_fake_editor &&
-	FAKE_COMMIT_AMEND="NEVER" FAKE_LINES="1 fixup 2 fixup 3 fixup 4" \
-		git rebase -i $base &&
+	(
+		set_fake_editor &&
+		FAKE_COMMIT_AMEND="NEVER" \
+			FAKE_LINES="1 fixup 2 fixup 3 fixup 4" \
+			git rebase -i $base
+	) &&
 	test $base = $(git rev-parse HEAD^) &&
 	test 0 = $(git show | grep NEVER | wc -l) &&
 	git checkout @{-1} &&
@@ -465,12 +477,15 @@ test_expect_success C_LOCALE_OUTPUT 'multi-fixup does not fire up editor' '
 test_expect_success 'commit message used after conflict' '
 	git checkout -b conflict-fixup conflict-branch &&
 	base=$(git rev-parse HEAD~4) &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 fixup 3 fixup 4" git rebase -i $base &&
-	echo three > conflict &&
-	git add conflict &&
-	FAKE_COMMIT_AMEND="ONCE" EXPECT_HEADER_COUNT=2 \
-		git rebase --continue &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 fixup 3 fixup 4" \
+			git rebase -i $base &&
+		echo three > conflict &&
+		git add conflict &&
+		FAKE_COMMIT_AMEND="ONCE" EXPECT_HEADER_COUNT=2 \
+			git rebase --continue
+	) &&
 	test $base = $(git rev-parse HEAD^) &&
 	test 1 = $(git show | grep ONCE | wc -l) &&
 	git checkout @{-1} &&
@@ -480,12 +495,15 @@ test_expect_success 'commit message used after conflict' '
 test_expect_success 'commit message retained after conflict' '
 	git checkout -b conflict-squash conflict-branch &&
 	base=$(git rev-parse HEAD~4) &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 fixup 3 squash 4" git rebase -i $base &&
-	echo three > conflict &&
-	git add conflict &&
-	FAKE_COMMIT_AMEND="TWICE" EXPECT_HEADER_COUNT=2 \
-		git rebase --continue &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 fixup 3 squash 4" \
+			git rebase -i $base &&
+		echo three > conflict &&
+		git add conflict &&
+		FAKE_COMMIT_AMEND="TWICE" EXPECT_HEADER_COUNT=2 \
+			git rebase --continue
+	) &&
 	test $base = $(git rev-parse HEAD^) &&
 	test 2 = $(git show | grep TWICE | wc -l) &&
 	git checkout @{-1} &&
@@ -502,10 +520,13 @@ test_expect_success C_LOCALE_OUTPUT 'squash and fixup generate correct log messa
 	EOF
 	git checkout -b squash-fixup E &&
 	base=$(git rev-parse HEAD~4) &&
-	set_fake_editor &&
-	FAKE_COMMIT_AMEND="ONCE" FAKE_LINES="1 fixup 2 squash 3 fixup 4" \
-		EXPECT_HEADER_COUNT=4 \
-		git rebase -i $base &&
+	(
+		set_fake_editor &&
+		FAKE_COMMIT_AMEND="ONCE" \
+			FAKE_LINES="1 fixup 2 squash 3 fixup 4" \
+			EXPECT_HEADER_COUNT=4 \
+			git rebase -i $base
+	) &&
 	git cat-file commit HEAD | sed -e 1,/^\$/d > actual-squash-fixup &&
 	test_cmp expect-squash-fixup actual-squash-fixup &&
 	git cat-file commit HEAD@{2} |
@@ -519,10 +540,13 @@ test_expect_success C_LOCALE_OUTPUT 'squash and fixup generate correct log messa
 test_expect_success C_LOCALE_OUTPUT 'squash ignores comments' '
 	git checkout -b skip-comments E &&
 	base=$(git rev-parse HEAD~4) &&
-	set_fake_editor &&
-	FAKE_COMMIT_AMEND="ONCE" FAKE_LINES="# 1 # squash 2 # squash 3 # squash 4 #" \
-		EXPECT_HEADER_COUNT=4 \
-		git rebase -i $base &&
+	(
+		set_fake_editor &&
+		FAKE_COMMIT_AMEND="ONCE" \
+			FAKE_LINES="# 1 # squash 2 # squash 3 # squash 4 #" \
+			EXPECT_HEADER_COUNT=4 \
+			git rebase -i $base
+	) &&
 	test $base = $(git rev-parse HEAD^) &&
 	test 1 = $(git show | grep ONCE | wc -l) &&
 	git checkout @{-1} &&
@@ -532,10 +556,13 @@ test_expect_success C_LOCALE_OUTPUT 'squash ignores comments' '
 test_expect_success C_LOCALE_OUTPUT 'squash ignores blank lines' '
 	git checkout -b skip-blank-lines E &&
 	base=$(git rev-parse HEAD~4) &&
-	set_fake_editor &&
-	FAKE_COMMIT_AMEND="ONCE" FAKE_LINES="> 1 > squash 2 > squash 3 > squash 4 >" \
-		EXPECT_HEADER_COUNT=4 \
-		git rebase -i $base &&
+	(
+		set_fake_editor &&
+		FAKE_COMMIT_AMEND="ONCE" \
+			FAKE_LINES="> 1 > squash 2 > squash 3 > squash 4 >" \
+			EXPECT_HEADER_COUNT=4 \
+			git rebase -i $base
+	) &&
 	test $base = $(git rev-parse HEAD^) &&
 	test 1 = $(git show | grep ONCE | wc -l) &&
 	git checkout @{-1} &&
@@ -545,17 +572,21 @@ test_expect_success C_LOCALE_OUTPUT 'squash ignores blank lines' '
 test_expect_success 'squash works as expected' '
 	git checkout -b squash-works no-conflict-branch &&
 	one=$(git rev-parse HEAD~3) &&
-	set_fake_editor &&
-	FAKE_LINES="1 s 3 2" EXPECT_HEADER_COUNT=2 \
-		git rebase -i HEAD~3 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 s 3 2" EXPECT_HEADER_COUNT=2 git rebase -i HEAD~3
+	) &&
 	test $one = $(git rev-parse HEAD~2)
 '
 
 test_expect_success 'interrupted squash works as expected' '
 	git checkout -b interrupted-squash conflict-branch &&
 	one=$(git rev-parse HEAD~3) &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 squash 3 2" git rebase -i HEAD~3 &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 squash 3 2" \
+			git rebase -i HEAD~3
+	) &&
 	test_write_lines one two four > conflict &&
 	git add conflict &&
 	test_must_fail git rebase --continue &&
@@ -568,8 +599,11 @@ test_expect_success 'interrupted squash works as expected' '
 test_expect_success 'interrupted squash works as expected (case 2)' '
 	git checkout -b interrupted-squash2 conflict-branch &&
 	one=$(git rev-parse HEAD~3) &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="3 squash 1 2" git rebase -i HEAD~3 &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="3 squash 1 2" \
+			git rebase -i HEAD~3
+	) &&
 	test_write_lines one four > conflict &&
 	git add conflict &&
 	test_must_fail git rebase --continue &&
@@ -589,11 +623,13 @@ test_expect_success '--continue tries to commit, even for "edit"' '
 	git commit -m "unrelated change" &&
 	parent=$(git rev-parse HEAD^) &&
 	test_tick &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1" git rebase -i HEAD^ &&
-	echo edited > file7 &&
-	git add file7 &&
-	FAKE_COMMIT_MESSAGE="chouette!" git rebase --continue &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1" git rebase -i HEAD^ &&
+		echo edited > file7 &&
+		git add file7 &&
+		FAKE_COMMIT_MESSAGE="chouette!" git rebase --continue
+	) &&
 	test edited = $(git show HEAD:file7) &&
 	git show HEAD | grep chouette &&
 	test $parent = $(git rev-parse HEAD^)
@@ -602,34 +638,41 @@ test_expect_success '--continue tries to commit, even for "edit"' '
 test_expect_success 'aborted --continue does not squash commits after "edit"' '
 	old=$(git rev-parse HEAD) &&
 	test_tick &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1" git rebase -i HEAD^ &&
-	echo "edited again" > file7 &&
-	git add file7 &&
-	test_must_fail env FAKE_COMMIT_MESSAGE=" " git rebase --continue &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1" git rebase -i HEAD^ &&
+		echo "edited again" > file7 &&
+		git add file7 &&
+		test_must_fail env FAKE_COMMIT_MESSAGE=" " git rebase --continue
+	) &&
 	test $old = $(git rev-parse HEAD) &&
 	git rebase --abort
 '
 
 test_expect_success 'auto-amend only edited commits after "edit"' '
 	test_tick &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1" git rebase -i HEAD^ &&
-	echo "edited again" > file7 &&
-	git add file7 &&
-	FAKE_COMMIT_MESSAGE="edited file7 again" git commit &&
-	echo "and again" > file7 &&
-	git add file7 &&
-	test_tick &&
-	test_must_fail env FAKE_COMMIT_MESSAGE="and again" git rebase --continue &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1" git rebase -i HEAD^ &&
+		echo "edited again" > file7 &&
+		git add file7 &&
+		FAKE_COMMIT_MESSAGE="edited file7 again" git commit &&
+		echo "and again" > file7 &&
+		git add file7 &&
+		test_tick &&
+		test_must_fail env FAKE_COMMIT_MESSAGE="and again" \
+			git rebase --continue
+	) &&
 	git rebase --abort
 '
 
 test_expect_success 'clean error after failed "exec"' '
 	test_tick &&
 	test_when_finished "git rebase --abort || :" &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 exec_false" git rebase -i HEAD^ &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 exec_false" git rebase -i HEAD^
+	) &&
 	echo "edited again" > file7 &&
 	git add file7 &&
 	test_must_fail git rebase --continue 2>error &&
@@ -640,8 +683,10 @@ test_expect_success 'rebase a detached HEAD' '
 	grandparent=$(git rev-parse HEAD~2) &&
 	git checkout $(git rev-parse HEAD) &&
 	test_tick &&
-	set_fake_editor &&
-	FAKE_LINES="2 1" git rebase -i HEAD~2 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="2 1" git rebase -i HEAD~2
+	) &&
 	test $grandparent = $(git rev-parse HEAD~2)
 '
 
@@ -656,9 +701,10 @@ test_expect_success 'rebase a commit violating pre-commit' '
 	test_must_fail git commit -m doesnt-verify file1 &&
 	git commit -m doesnt-verify --no-verify file1 &&
 	test_tick &&
-	set_fake_editor &&
-	FAKE_LINES=2 git rebase -i HEAD~2
-
+	(
+		set_fake_editor &&
+		FAKE_LINES=2 git rebase -i HEAD~2
+	)
 '
 
 test_expect_success 'rebase with a file named HEAD in worktree' '
@@ -678,8 +724,10 @@ test_expect_success 'rebase with a file named HEAD in worktree' '
 		git commit -m "Add body"
 	) &&
 
-	set_fake_editor &&
-	FAKE_LINES="1 squash 2" git rebase -i @{-1} &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 squash 2" git rebase -i @{-1}
+	) &&
 	test "$(git show -s --pretty=format:%an)" = "Squashed Away"
 
 '
@@ -690,9 +738,8 @@ test_expect_success 'do "noop" when there is nothing to cherry-pick' '
 	GIT_EDITOR=: git commit --amend \
 		--author="Somebody else <somebody@else.com>" &&
 	test $(git rev-parse branch3) != $(git rev-parse branch4) &&
-	set_fake_editor &&
 	git rebase -i branch3 &&
-	test $(git rev-parse branch3) = $(git rev-parse branch4)
+	test_cmp_rev branch3 branch4
 
 '
 
@@ -715,13 +762,14 @@ test_expect_success 'submodule rebase setup' '
 		git commit -a -m "submodule second"
 	) &&
 	test_tick &&
-	set_fake_editor &&
 	git commit -a -m "Three changes submodule"
 '
 
 test_expect_success 'submodule rebase -i' '
-	set_fake_editor &&
-	FAKE_LINES="1 squash 2 3" git rebase -i A
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 squash 2 3" git rebase -i A
+	)
 '
 
 test_expect_success 'submodule conflict setup' '
@@ -738,7 +786,6 @@ test_expect_success 'submodule conflict setup' '
 '
 
 test_expect_success 'rebase -i continue with only submodule staged' '
-	set_fake_editor &&
 	test_must_fail git rebase -i submodule-base &&
 	git add sub &&
 	git rebase --continue &&
@@ -748,11 +795,10 @@ test_expect_success 'rebase -i continue with only submodule staged' '
 test_expect_success 'rebase -i continue with unstaged submodule' '
 	git checkout submodule-topic &&
 	git reset --hard &&
-	set_fake_editor &&
 	test_must_fail git rebase -i submodule-base &&
 	git reset &&
 	git rebase --continue &&
-	test $(git rev-parse submodule-base) = $(git rev-parse HEAD)
+	test_cmp_rev submodule-base HEAD
 '
 
 test_expect_success 'avoid unnecessary reset' '
@@ -761,7 +807,6 @@ test_expect_success 'avoid unnecessary reset' '
 	test-tool chmtime =123456789 file3 &&
 	git update-index --refresh &&
 	HEAD=$(git rev-parse HEAD) &&
-	set_fake_editor &&
 	git rebase -i HEAD~4 &&
 	test $HEAD = $(git rev-parse HEAD) &&
 	MTIME=$(test-tool chmtime --get file3) &&
@@ -770,16 +815,22 @@ test_expect_success 'avoid unnecessary reset' '
 
 test_expect_success 'reword' '
 	git checkout -b reword-branch master &&
-	set_fake_editor &&
-	FAKE_LINES="1 2 3 reword 4" FAKE_COMMIT_MESSAGE="E changed" git rebase -i A &&
-	git show HEAD | grep "E changed" &&
-	test $(git rev-parse master) != $(git rev-parse HEAD) &&
-	test $(git rev-parse master^) = $(git rev-parse HEAD^) &&
-	FAKE_LINES="1 2 reword 3 4" FAKE_COMMIT_MESSAGE="D changed" git rebase -i A &&
-	git show HEAD^ | grep "D changed" &&
-	FAKE_LINES="reword 1 2 3 4" FAKE_COMMIT_MESSAGE="B changed" git rebase -i A &&
-	git show HEAD~3 | grep "B changed" &&
-	FAKE_LINES="1 r 2 pick 3 p 4" FAKE_COMMIT_MESSAGE="C changed" git rebase -i A &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 2 3 reword 4" FAKE_COMMIT_MESSAGE="E changed" \
+			git rebase -i A &&
+		git show HEAD | grep "E changed" &&
+		test $(git rev-parse master) != $(git rev-parse HEAD) &&
+		test_cmp_rev master^ HEAD^ &&
+		FAKE_LINES="1 2 reword 3 4" FAKE_COMMIT_MESSAGE="D changed" \
+			git rebase -i A &&
+		git show HEAD^ | grep "D changed" &&
+		FAKE_LINES="reword 1 2 3 4" FAKE_COMMIT_MESSAGE="B changed" \
+			git rebase -i A &&
+		git show HEAD~3 | grep "B changed" &&
+		FAKE_LINES="1 r 2 pick 3 p 4" FAKE_COMMIT_MESSAGE="C changed" \
+			git rebase -i A
+	) &&
 	git show HEAD~2 | grep "C changed"
 '
 
@@ -790,7 +841,6 @@ test_expect_success 'rebase -i can copy notes' '
 	test_commit n2 &&
 	test_commit n3 &&
 	git notes add -m"a note" n3 &&
-	set_fake_editor &&
 	git rebase -i --onto n1 n2 &&
 	test "a note" = "$(git notes show HEAD)"
 '
@@ -803,8 +853,11 @@ test_expect_success 'rebase -i can copy notes over a fixup' '
 	EOF
 	git reset --hard n3 &&
 	git notes add -m"an earlier note" n2 &&
-	set_fake_editor &&
-	GIT_NOTES_REWRITE_MODE=concatenate FAKE_LINES="1 f 2" git rebase -i n1 &&
+	(
+		set_fake_editor &&
+		GIT_NOTES_REWRITE_MODE=concatenate FAKE_LINES="1 f 2" \
+			git rebase -i n1
+	) &&
 	git notes show > output &&
 	test_cmp expect output
 '
@@ -813,8 +866,10 @@ test_expect_success 'rebase while detaching HEAD' '
 	git symbolic-ref HEAD &&
 	grandparent=$(git rev-parse HEAD~2) &&
 	test_tick &&
-	set_fake_editor &&
-	FAKE_LINES="2 1" git rebase -i HEAD~2 HEAD^0 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="2 1" git rebase -i HEAD~2 HEAD^0
+	) &&
 	test $grandparent = $(git rev-parse HEAD~2) &&
 	test_must_fail git symbolic-ref HEAD
 '
@@ -823,7 +878,6 @@ test_tick # Ensure that the rebased commits get a different timestamp.
 test_expect_success 'always cherry-pick with --no-ff' '
 	git checkout no-ff-branch &&
 	git tag original-no-ff-branch &&
-	set_fake_editor &&
 	git rebase -i --no-ff A &&
 	for p in 0 1 2
 	do
@@ -831,7 +885,7 @@ test_expect_success 'always cherry-pick with --no-ff' '
 		git diff HEAD~$p original-no-ff-branch~$p > out &&
 		test_must_be_empty out
 	done &&
-	test $(git rev-parse HEAD~3) = $(git rev-parse original-no-ff-branch~3) &&
+	test_cmp_rev HEAD~3 original-no-ff-branch~3 &&
 	git diff HEAD~3 original-no-ff-branch~3 > out &&
 	test_must_be_empty out
 '
@@ -855,8 +909,10 @@ test_expect_success 'set up commits with funny messages' '
 test_expect_success 'rebase-i history with funny messages' '
 	git rev-list A..funny >expect &&
 	test_tick &&
-	set_fake_editor &&
-	FAKE_LINES="1 2 3 4" git rebase -i A &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 2 3 4" git rebase -i A
+	) &&
 	git rev-list A.. >actual &&
 	test_cmp expect actual
 '
@@ -870,9 +926,9 @@ test_expect_success 'prepare for rebase -i --exec' '
 '
 
 test_expect_success 'running "git rebase -i --exec git show HEAD"' '
-	set_fake_editor &&
-	git rebase -i --exec "git show HEAD" HEAD~2 >actual &&
 	(
+		set_fake_editor &&
+		git rebase -i --exec "git show HEAD" HEAD~2 >actual &&
 		FAKE_LINES="1 exec_git_show_HEAD 2 exec_git_show_HEAD" &&
 		export FAKE_LINES &&
 		git rebase -i HEAD~2 >expect
@@ -883,9 +939,9 @@ test_expect_success 'running "git rebase -i --exec git show HEAD"' '
 
 test_expect_success 'running "git rebase --exec git show HEAD -i"' '
 	git reset --hard execute &&
-	set_fake_editor &&
-	git rebase --exec "git show HEAD" -i HEAD~2 >actual &&
 	(
+		set_fake_editor &&
+		git rebase --exec "git show HEAD" -i HEAD~2 >actual &&
 		FAKE_LINES="1 exec_git_show_HEAD 2 exec_git_show_HEAD" &&
 		export FAKE_LINES &&
 		git rebase -i HEAD~2 >expect
@@ -896,9 +952,9 @@ test_expect_success 'running "git rebase --exec git show HEAD -i"' '
 
 test_expect_success 'running "git rebase -ix git show HEAD"' '
 	git reset --hard execute &&
-	set_fake_editor &&
-	git rebase -ix "git show HEAD" HEAD~2 >actual &&
 	(
+		set_fake_editor &&
+		git rebase -ix "git show HEAD" HEAD~2 >actual &&
 		FAKE_LINES="1 exec_git_show_HEAD 2 exec_git_show_HEAD" &&
 		export FAKE_LINES &&
 		git rebase -i HEAD~2 >expect
@@ -910,9 +966,9 @@ test_expect_success 'running "git rebase -ix git show HEAD"' '
 
 test_expect_success 'rebase -ix with several <CMD>' '
 	git reset --hard execute &&
-	set_fake_editor &&
-	git rebase -ix "git show HEAD; pwd" HEAD~2 >actual &&
 	(
+		set_fake_editor &&
+		git rebase -ix "git show HEAD; pwd" HEAD~2 >actual &&
 		FAKE_LINES="1 exec_git_show_HEAD;_pwd 2 exec_git_show_HEAD;_pwd" &&
 		export FAKE_LINES &&
 		git rebase -i HEAD~2 >expect
@@ -923,9 +979,9 @@ test_expect_success 'rebase -ix with several <CMD>' '
 
 test_expect_success 'rebase -ix with several instances of --exec' '
 	git reset --hard execute &&
-	set_fake_editor &&
-	git rebase -i --exec "git show HEAD" --exec "pwd" HEAD~2 >actual &&
 	(
+		set_fake_editor &&
+		git rebase -i --exec "git show HEAD" --exec "pwd" HEAD~2 >actual &&
 		FAKE_LINES="1 exec_git_show_HEAD exec_pwd 2
 				exec_git_show_HEAD exec_pwd" &&
 		export FAKE_LINES &&
@@ -944,13 +1000,11 @@ test_expect_success C_LOCALE_OUTPUT 'rebase -ix with --autosquash' '
 	echo bis >bis.txt &&
 	git add bis.txt &&
 	git commit -m "fixup! two_exec" &&
-	set_fake_editor &&
-	(
-		git checkout -b autosquash_actual &&
-		git rebase -i --exec "git show HEAD" --autosquash HEAD~4 >actual
-	) &&
+	git checkout -b autosquash_actual &&
+	git rebase -i --exec "git show HEAD" --autosquash HEAD~4 >actual &&
 	git checkout autosquash &&
 	(
+		set_fake_editor &&
 		git checkout -b autosquash_expected &&
 		FAKE_LINES="1 fixup 3 fixup 4 exec_git_show_HEAD 2 exec_git_show_HEAD" &&
 		export FAKE_LINES &&
@@ -971,7 +1025,6 @@ test_expect_success 'rebase --exec works without -i ' '
 
 test_expect_success 'rebase -i --exec without <CMD>' '
 	git reset --hard execute &&
-	set_fake_editor &&
 	test_must_fail git rebase -i --exec 2>actual &&
 	test_i18ngrep "requires a value" actual &&
 	git checkout master
@@ -979,8 +1032,10 @@ test_expect_success 'rebase -i --exec without <CMD>' '
 
 test_expect_success 'rebase -i --root re-order and drop commits' '
 	git checkout E &&
-	set_fake_editor &&
-	FAKE_LINES="3 1 2 5" git rebase -i --root &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="3 1 2 5" git rebase -i --root
+	) &&
 	test E = $(git cat-file commit HEAD | sed -ne \$p) &&
 	test B = $(git cat-file commit HEAD^ | sed -ne \$p) &&
 	test A = $(git cat-file commit HEAD^^ | sed -ne \$p) &&
@@ -993,39 +1048,59 @@ test_expect_success 'rebase -i --root retain root commit author and message' '
 	echo B >file7 &&
 	git add file7 &&
 	GIT_AUTHOR_NAME="Twerp Snog" git commit -m "different author" &&
-	set_fake_editor &&
-	FAKE_LINES="2" git rebase -i --root &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="2" git rebase -i --root
+	) &&
 	git cat-file commit HEAD | grep -q "^author Twerp Snog" &&
 	git cat-file commit HEAD | grep -q "^different author$"
 '
 
 test_expect_success 'rebase -i --root temporary sentinel commit' '
 	git checkout B &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="2" git rebase -i --root &&
-	git cat-file commit HEAD | grep "^tree 4b825dc642cb" &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="2" git rebase -i --root
+	) &&
+	git cat-file commit HEAD | grep "^tree $EMPTY_TREE" &&
 	git rebase --abort
 '
 
 test_expect_success 'rebase -i --root fixup root commit' '
 	git checkout B &&
-	set_fake_editor &&
-	FAKE_LINES="1 fixup 2" git rebase -i --root &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 fixup 2" git rebase -i --root
+	) &&
 	test A = $(git cat-file commit HEAD | sed -ne \$p) &&
 	test B = $(git show HEAD:file1) &&
 	test 0 = $(git cat-file commit HEAD | grep -c ^parent\ )
 '
 
-test_expect_success 'rebase -i --root reword root commit' '
+test_expect_success 'rebase -i --root reword original root commit' '
 	test_when_finished "test_might_fail git rebase --abort" &&
-	git checkout -b reword-root-branch master &&
-	set_fake_editor &&
-	FAKE_LINES="reword 1 2" FAKE_COMMIT_MESSAGE="A changed" \
-	git rebase -i --root &&
+	git checkout -b reword-original-root-branch master &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="reword 1 2" FAKE_COMMIT_MESSAGE="A changed" \
+			git rebase -i --root
+	) &&
 	git show HEAD^ | grep "A changed" &&
 	test -z "$(git show -s --format=%p HEAD^)"
 '
 
+test_expect_success 'rebase -i --root reword new root commit' '
+	test_when_finished "test_might_fail git rebase --abort" &&
+	git checkout -b reword-now-root-branch master &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="reword 3 1" FAKE_COMMIT_MESSAGE="C changed" \
+		git rebase -i --root
+	) &&
+	git show HEAD^ | grep "C changed" &&
+	test -z "$(git show -s --format=%p HEAD^)"
+'
+
 test_expect_success 'rebase -i --root when root has untracked file conflict' '
 	test_when_finished "reset_rebase" &&
 	git checkout -b failing-root-pick A &&
@@ -1033,8 +1108,10 @@ test_expect_success 'rebase -i --root when root has untracked file conflict' '
 	git rm file1 &&
 	git commit -m "remove file 1 add file 2" &&
 	echo z >file1 &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 2" git rebase -i --root &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 2" git rebase -i --root
+	) &&
 	rm file1 &&
 	git rebase --continue &&
 	test "$(git log -1 --format=%B)" = "remove file 1 add file 2" &&
@@ -1044,32 +1121,38 @@ test_expect_success 'rebase -i --root when root has untracked file conflict' '
 test_expect_success 'rebase -i --root reword root when root has untracked file conflict' '
 	test_when_finished "reset_rebase" &&
 	echo z>file1 &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="reword 1 2" \
-		FAKE_COMMIT_MESSAGE="Modified A" git rebase -i --root &&
-	rm file1 &&
-	FAKE_COMMIT_MESSAGE="Reworded A" git rebase --continue &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="reword 1 2" \
+			FAKE_COMMIT_MESSAGE="Modified A" git rebase -i --root &&
+		rm file1 &&
+		FAKE_COMMIT_MESSAGE="Reworded A" git rebase --continue
+	) &&
 	test "$(git log -1 --format=%B HEAD^)" = "Reworded A" &&
 	test "$(git rev-list --count HEAD)" = 2
 '
 
 test_expect_success C_LOCALE_OUTPUT 'rebase --edit-todo does not work on non-interactive rebase' '
-	git checkout reword-root-branch &&
+	git checkout reword-original-root-branch &&
 	git reset --hard &&
 	git checkout conflict-branch &&
-	set_fake_editor &&
-	test_must_fail git rebase --onto HEAD~2 HEAD~ &&
-	test_must_fail git rebase --edit-todo &&
+	(
+		set_fake_editor &&
+		test_must_fail git rebase -f --apply --onto HEAD~2 HEAD~ &&
+		test_must_fail git rebase --edit-todo
+	) &&
 	git rebase --abort
 '
 
 test_expect_success 'rebase --edit-todo can be used to modify todo' '
 	git reset --hard &&
 	git checkout no-conflict-branch^0 &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1 2 3" git rebase -i HEAD~3 &&
-	FAKE_LINES="2 1" git rebase --edit-todo &&
-	git rebase --continue &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1 2 3" git rebase -i HEAD~3 &&
+		FAKE_LINES="2 1" git rebase --edit-todo &&
+		git rebase --continue
+	) &&
 	test M = $(git cat-file commit HEAD^ | sed -ne \$p) &&
 	test L = $(git cat-file commit HEAD | sed -ne \$p)
 '
@@ -1077,13 +1160,12 @@ test_expect_success 'rebase --edit-todo can be used to modify todo' '
 test_expect_success 'rebase -i produces readable reflog' '
 	git reset --hard &&
 	git branch -f branch-reflog-test H &&
-	set_fake_editor &&
 	git rebase -i --onto I F branch-reflog-test &&
 	cat >expect <<-\EOF &&
-	rebase -i (finish): returning to refs/heads/branch-reflog-test
-	rebase -i (pick): H
-	rebase -i (pick): G
-	rebase -i (start): checkout I
+	rebase (finish): returning to refs/heads/branch-reflog-test
+	rebase (pick): H
+	rebase (pick): G
+	rebase (start): checkout I
 	EOF
 	git reflog -n4 HEAD |
 	sed "s/[^:]*: //" >actual &&
@@ -1098,8 +1180,10 @@ test_expect_success 'rebase -i respects core.commentchar' '
 	sed -e "2,\$s/^/\\\\/" "$1" >"$1.tmp" &&
 	mv "$1.tmp" "$1"
 	EOF
-	test_set_editor "$(pwd)/remove-all-but-first.sh" &&
-	git rebase -i B &&
+	(
+		test_set_editor "$(pwd)/remove-all-but-first.sh" &&
+		git rebase -i B
+	) &&
 	test B = $(git cat-file commit HEAD^ | sed -ne \$p)
 '
 
@@ -1108,9 +1192,11 @@ test_expect_success 'rebase -i respects core.commentchar=auto' '
 	write_script copy-edit-script.sh <<-\EOF &&
 	cp "$1" edit-script
 	EOF
-	test_set_editor "$(pwd)/copy-edit-script.sh" &&
 	test_when_finished "git rebase --abort || :" &&
-	git rebase -i HEAD^ &&
+	(
+		test_set_editor "$(pwd)/copy-edit-script.sh" &&
+		git rebase -i HEAD^
+	) &&
 	test -z "$(grep -ve "^#" -e "^\$" -e "^pick" edit-script)"
 '
 
@@ -1145,8 +1231,11 @@ test_expect_success 'interrupted rebase -i with --strategy and -X' '
 	echo five >conflict &&
 	echo Z >file1 &&
 	git commit -a -m "one file conflict" &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1 2" git rebase -i --strategy=recursive -Xours conflict-branch &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1 2" git rebase -i --strategy=recursive \
+			-Xours conflict-branch
+	) &&
 	git rebase --continue &&
 	test $(git show conflict-branch:conflict) = $(cat conflict) &&
 	test $(cat file1) = Z
@@ -1161,7 +1250,7 @@ test_expect_success 'rebase -i error on commits with \ in message' '
 	test_expect_code 1 grep  "	emp" error
 '
 
-test_expect_success 'short SHA-1 setup' '
+test_expect_success 'short commit ID setup' '
 	test_when_finished "git checkout master" &&
 	git checkout --orphan collide &&
 	git rm -rf . &&
@@ -1173,22 +1262,68 @@ test_expect_success 'short SHA-1 setup' '
 	)
 '
 
-test_expect_success 'short SHA-1 collide' '
+if test -n "$GIT_TEST_FIND_COLLIDER"
+then
+	author="$(unset test_tick; test_tick; git var GIT_AUTHOR_IDENT)"
+	committer="$(unset test_tick; test_tick; git var GIT_COMMITTER_IDENT)"
+	blob="$(git rev-parse collide2:collide)"
+	from="$(git rev-parse collide1^0)"
+	repl="commit refs/heads/collider-&\\n"
+	repl="${repl}author $author\\ncommitter $committer\\n"
+	repl="${repl}data <<EOF\\ncollide2 &\\nEOF\\n"
+	repl="${repl}from $from\\nM 100644 $blob collide\\n"
+	test_seq 1 32768 | sed "s|.*|$repl|" >script &&
+	git fast-import <script &&
+	git pack-refs &&
+	git for-each-ref >refs &&
+	grep "^$(test_oid t3404_collision)" <refs >matches &&
+	cat matches &&
+	test_line_count -gt 2 matches || {
+		echo "Could not find a collider" >&2
+		exit 1
+	}
+fi
+
+test_expect_success 'short commit ID collide' '
+	test_oid_cache <<-EOF &&
+	# collision-related constants
+	t3404_collision	sha1:6bcd
+	t3404_collision	sha256:0161
+	t3404_collider	sha1:ac4f2ee
+	t3404_collider	sha256:16697
+	EOF
 	test_when_finished "reset_rebase && git checkout master" &&
 	git checkout collide &&
+	colliding_id=$(test_oid t3404_collision) &&
+	hexsz=$(test_oid hexsz) &&
+	test $colliding_id = "$(git rev-parse HEAD | cut -c 1-4)" &&
+	test_config core.abbrev 4 &&
 	(
-	unset test_tick &&
-	test_tick &&
-	set_fake_editor &&
-	FAKE_COMMIT_MESSAGE="collide2 ac4f2ee" \
-	FAKE_LINES="reword 1 2" git rebase -i HEAD~2
-	)
+		unset test_tick &&
+		test_tick &&
+		set_fake_editor &&
+		FAKE_COMMIT_MESSAGE="collide2 $(test_oid t3404_collider)" \
+		FAKE_LINES="reword 1 break 2" git rebase -i HEAD~2 &&
+		test $colliding_id = "$(git rev-parse HEAD | cut -c 1-4)" &&
+		grep "^pick $colliding_id " \
+			.git/rebase-merge/git-rebase-todo.tmp &&
+		grep "^pick [0-9a-f]\{$hexsz\}" \
+			.git/rebase-merge/git-rebase-todo &&
+		grep "^pick [0-9a-f]\{$hexsz\}" \
+			.git/rebase-merge/git-rebase-todo.backup &&
+		git rebase --continue
+	) &&
+	collide2="$(git rev-parse HEAD~1 | cut -c 1-4)" &&
+	collide3="$(git rev-parse collide3 | cut -c 1-4)" &&
+	test "$collide2" = "$collide3"
 '
 
 test_expect_success 'respect core.abbrev' '
 	git config core.abbrev 12 &&
-	set_cat_todo_editor &&
-	test_must_fail git rebase -i HEAD~4 >todo-list &&
+	(
+		set_cat_todo_editor &&
+		test_must_fail git rebase -i HEAD~4 >todo-list
+	) &&
 	test 4 = $(grep -c "pick [0-9a-f]\{12,\}" todo-list)
 '
 
@@ -1196,16 +1331,20 @@ test_expect_success 'todo count' '
 	write_script dump-raw.sh <<-\EOF &&
 		cat "$1"
 	EOF
-	test_set_editor "$(pwd)/dump-raw.sh" &&
-	git rebase -i HEAD~4 >actual &&
+	(
+		test_set_editor "$(pwd)/dump-raw.sh" &&
+		git rebase -i HEAD~4 >actual
+	) &&
 	test_i18ngrep "^# Rebase ..* onto ..* ([0-9]" actual
 '
 
 test_expect_success 'rebase -i commits that overwrite untracked files (pick)' '
 	git checkout --force branch2 &&
 	git clean -f &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1 2" git rebase -i A &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1 2" git rebase -i A
+	) &&
 	test_cmp_rev HEAD F &&
 	test_path_is_missing file6 &&
 	>file6 &&
@@ -1220,8 +1359,10 @@ test_expect_success 'rebase -i commits that overwrite untracked files (squash)'
 	git checkout --force branch2 &&
 	git clean -f &&
 	git tag original-branch2 &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1 squash 2" git rebase -i A &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1 squash 2" git rebase -i A
+	) &&
 	test_cmp_rev HEAD F &&
 	test_path_is_missing file6 &&
 	>file6 &&
@@ -1236,8 +1377,10 @@ test_expect_success 'rebase -i commits that overwrite untracked files (squash)'
 test_expect_success 'rebase -i commits that overwrite untracked files (no ff)' '
 	git checkout --force branch2 &&
 	git clean -f &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1 2" git rebase -i --no-ff A &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1 2" git rebase -i --no-ff A
+	) &&
 	test $(git cat-file commit HEAD | sed -ne \$p) = F &&
 	test_path_is_missing file6 &&
 	>file6 &&
@@ -1260,8 +1403,10 @@ test_expect_success 'rebase --continue removes CHERRY_PICK_HEAD' '
 	git tag seq-onto &&
 	git reset --hard HEAD~2 &&
 	git cherry-pick seq-onto &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES= git rebase -i seq-onto &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES= git rebase -i seq-onto
+	) &&
 	test -d .git/rebase-merge &&
 	git rebase --continue &&
 	git diff --exit-code seq-onto &&
@@ -1280,8 +1425,10 @@ rebase_setup_and_clean () {
 
 test_expect_success 'drop' '
 	rebase_setup_and_clean drop-test &&
-	set_fake_editor &&
-	FAKE_LINES="1 drop 2 3 d 4 5" git rebase -i --root &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 drop 2 3 d 4 5" git rebase -i --root
+	) &&
 	test E = $(git cat-file commit HEAD | sed -ne \$p) &&
 	test C = $(git cat-file commit HEAD^ | sed -ne \$p) &&
 	test A = $(git cat-file commit HEAD^^ | sed -ne \$p)
@@ -1290,9 +1437,10 @@ test_expect_success 'drop' '
 test_expect_success 'rebase -i respects rebase.missingCommitsCheck = ignore' '
 	test_config rebase.missingCommitsCheck ignore &&
 	rebase_setup_and_clean missing-commit &&
-	set_fake_editor &&
-	FAKE_LINES="1 2 3 4" \
-		git rebase -i --root 2>actual &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 2 3 4" git rebase -i --root 2>actual
+	) &&
 	test D = $(git cat-file commit HEAD | sed -ne \$p) &&
 	test_i18ngrep \
 		"Successfully rebased and updated refs/heads/missing-commit" \
@@ -1308,9 +1456,10 @@ test_expect_success 'rebase -i respects rebase.missingCommitsCheck = warn' '
 	EOF
 	test_config rebase.missingCommitsCheck warn &&
 	rebase_setup_and_clean missing-commit &&
-	set_fake_editor &&
-	FAKE_LINES="1 2 3 4" \
-		git rebase -i --root 2>actual.2 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 2 3 4" git rebase -i --root 2>actual.2
+	) &&
 	head -n4 actual.2 >actual &&
 	test_i18ncmp expect actual &&
 	test D = $(git cat-file commit HEAD | sed -ne \$p)
@@ -1332,19 +1481,141 @@ test_expect_success 'rebase -i respects rebase.missingCommitsCheck = error' '
 	EOF
 	test_config rebase.missingCommitsCheck error &&
 	rebase_setup_and_clean missing-commit &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 2 4" \
-		git rebase -i --root 2>actual &&
-	test_i18ncmp expect actual &&
-	cp .git/rebase-merge/git-rebase-todo.backup \
-		.git/rebase-merge/git-rebase-todo &&
-	FAKE_LINES="1 2 drop 3 4 drop 5" \
-		git rebase --edit-todo &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 2 4" \
+			git rebase -i --root 2>actual &&
+		test_i18ncmp expect actual &&
+		cp .git/rebase-merge/git-rebase-todo.backup \
+			.git/rebase-merge/git-rebase-todo &&
+		FAKE_LINES="1 2 drop 3 4 drop 5" git rebase --edit-todo
+	) &&
 	git rebase --continue &&
 	test D = $(git cat-file commit HEAD | sed -ne \$p) &&
 	test B = $(git cat-file commit HEAD^ | sed -ne \$p)
 '
 
+test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = ignore' '
+	test_config rebase.missingCommitsCheck ignore &&
+	rebase_setup_and_clean missing-commit &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="break 1 2 3 4 5" git rebase -i --root &&
+		FAKE_LINES="1 2 3 4" git rebase --edit-todo &&
+		git rebase --continue 2>actual
+	) &&
+	test D = $(git cat-file commit HEAD | sed -ne \$p) &&
+	test_i18ngrep \
+		"Successfully rebased and updated refs/heads/missing-commit" \
+		actual
+'
+
+test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = warn' '
+	cat >expect <<-EOF &&
+	error: invalid line 1: badcmd $(git rev-list --pretty=oneline --abbrev-commit -1 master~4)
+	Warning: some commits may have been dropped accidentally.
+	Dropped commits (newer to older):
+	 - $(git rev-list --pretty=oneline --abbrev-commit -1 master)
+	 - $(git rev-list --pretty=oneline --abbrev-commit -1 master~4)
+	To avoid this message, use "drop" to explicitly remove a commit.
+	EOF
+	head -n4 expect >expect.2 &&
+	tail -n1 expect >>expect.2 &&
+	tail -n4 expect.2 >expect.3 &&
+	test_config rebase.missingCommitsCheck warn &&
+	rebase_setup_and_clean missing-commit &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="bad 1 2 3 4 5" \
+			git rebase -i --root &&
+		cp .git/rebase-merge/git-rebase-todo.backup orig &&
+		FAKE_LINES="2 3 4" git rebase --edit-todo 2>actual.2 &&
+		head -n6 actual.2 >actual &&
+		test_i18ncmp expect actual &&
+		cp orig .git/rebase-merge/git-rebase-todo &&
+		FAKE_LINES="1 2 3 4" git rebase --edit-todo 2>actual.2 &&
+		head -n4 actual.2 >actual &&
+		test_i18ncmp expect.3 actual &&
+		git rebase --continue 2>actual
+	) &&
+	test D = $(git cat-file commit HEAD | sed -ne \$p) &&
+	test_i18ngrep \
+		"Successfully rebased and updated refs/heads/missing-commit" \
+		actual
+'
+
+test_expect_success 'rebase --edit-todo respects rebase.missingCommitsCheck = error' '
+	cat >expect <<-EOF &&
+	error: invalid line 1: badcmd $(git rev-list --pretty=oneline --abbrev-commit -1 master~4)
+	Warning: some commits may have been dropped accidentally.
+	Dropped commits (newer to older):
+	 - $(git rev-list --pretty=oneline --abbrev-commit -1 master)
+	 - $(git rev-list --pretty=oneline --abbrev-commit -1 master~4)
+	To avoid this message, use "drop" to explicitly remove a commit.
+
+	Use '\''git config rebase.missingCommitsCheck'\'' to change the level of warnings.
+	The possible behaviours are: ignore, warn, error.
+
+	You can fix this with '\''git rebase --edit-todo'\'' and then run '\''git rebase --continue'\''.
+	Or you can abort the rebase with '\''git rebase --abort'\''.
+	EOF
+	tail -n11 expect >expect.2 &&
+	head -n3 expect.2 >expect.3 &&
+	tail -n7 expect.2 >>expect.3 &&
+	test_config rebase.missingCommitsCheck error &&
+	rebase_setup_and_clean missing-commit &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="bad 1 2 3 4 5" \
+			git rebase -i --root &&
+		cp .git/rebase-merge/git-rebase-todo.backup orig &&
+		test_must_fail env FAKE_LINES="2 3 4" \
+			git rebase --edit-todo 2>actual &&
+		test_i18ncmp expect actual &&
+		test_must_fail git rebase --continue 2>actual &&
+		test_i18ncmp expect.2 actual &&
+		test_must_fail git rebase --edit-todo &&
+		cp orig .git/rebase-merge/git-rebase-todo &&
+		test_must_fail env FAKE_LINES="1 2 3 4" \
+			git rebase --edit-todo 2>actual &&
+		test_i18ncmp expect.3 actual &&
+		test_must_fail git rebase --continue 2>actual &&
+		test_i18ncmp expect.3 actual &&
+		cp orig .git/rebase-merge/git-rebase-todo &&
+		FAKE_LINES="1 2 3 4 drop 5" git rebase --edit-todo &&
+		git rebase --continue 2>actual
+	) &&
+	test D = $(git cat-file commit HEAD | sed -ne \$p) &&
+	test_i18ngrep \
+		"Successfully rebased and updated refs/heads/missing-commit" \
+		actual
+'
+
+test_expect_success 'rebase.missingCommitsCheck = error after resolving conflicts' '
+	test_config rebase.missingCommitsCheck error &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="drop 1 break 2 3 4" git rebase -i A E
+	) &&
+	git rebase --edit-todo &&
+	test_must_fail git rebase --continue &&
+	echo x >file1 &&
+	git add file1 &&
+	git rebase --continue
+'
+
+test_expect_success 'rebase.missingCommitsCheck = error when editing for a second time' '
+	test_config rebase.missingCommitsCheck error &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 break 2 3" git rebase -i A D &&
+		cp .git/rebase-merge/git-rebase-todo todo &&
+		test_must_fail env FAKE_LINES=2 git rebase --edit-todo &&
+		GIT_SEQUENCE_EDITOR="cp todo" git rebase --edit-todo &&
+		git rebase --continue
+	)
+'
+
 test_expect_success 'respects rebase.abbreviateCommands with fixup, squash and exec' '
 	rebase_setup_and_clean abbrevcmd &&
 	test_commit "first" file1.txt "first line" first &&
@@ -1360,21 +1631,27 @@ test_expect_success 'respects rebase.abbreviateCommands with fixup, squash and e
 	x git show HEAD
 	EOF
 	git checkout abbrevcmd &&
-	set_cat_todo_editor &&
 	test_config rebase.abbreviateCommands true &&
-	test_must_fail git rebase -i --exec "git show HEAD" \
-		--autosquash master >actual &&
+	(
+		set_cat_todo_editor &&
+		test_must_fail git rebase -i --exec "git show HEAD" \
+			--autosquash master >actual
+	) &&
 	test_cmp expected actual
 '
 
 test_expect_success 'static check of bad command' '
 	rebase_setup_and_clean bad-cmd &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 2 3 bad 4 5" \
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 2 3 bad 4 5" \
 		git rebase -i --root 2>actual &&
-	test_i18ngrep "badcmd $(git rev-list --oneline -1 master~1)" actual &&
-	test_i18ngrep "You can fix this with .git rebase --edit-todo.." actual &&
-	FAKE_LINES="1 2 3 drop 4 5" git rebase --edit-todo &&
+		test_i18ngrep "badcmd $(git rev-list --oneline -1 master~1)" \
+				actual &&
+		test_i18ngrep "You can fix this with .git rebase --edit-todo.." \
+				actual &&
+		FAKE_LINES="1 2 3 drop 4 5" git rebase --edit-todo
+	) &&
 	git rebase --continue &&
 	test E = $(git cat-file commit HEAD | sed -ne \$p) &&
 	test C = $(git cat-file commit HEAD^ | sed -ne \$p)
@@ -1390,19 +1667,24 @@ test_expect_success 'tabs and spaces are accepted in the todolist' '
 	) >"$1.new"
 	mv "$1.new" "$1"
 	EOF
-	test_set_editor "$(pwd)/add-indent.sh" &&
-	git rebase -i HEAD^^^ &&
+	(
+		test_set_editor "$(pwd)/add-indent.sh" &&
+		git rebase -i HEAD^^^
+	) &&
 	test E = $(git cat-file commit HEAD | sed -ne \$p)
 '
 
 test_expect_success 'static check of bad SHA-1' '
 	rebase_setup_and_clean bad-sha &&
-	set_fake_editor &&
-	test_must_fail env FAKE_LINES="1 2 edit fakesha 3 4 5 #" \
-		git rebase -i --root 2>actual &&
-	test_i18ngrep "edit XXXXXXX False commit" actual &&
-	test_i18ngrep "You can fix this with .git rebase --edit-todo.." actual &&
-	FAKE_LINES="1 2 4 5 6" git rebase --edit-todo &&
+	(
+		set_fake_editor &&
+		test_must_fail env FAKE_LINES="1 2 edit fakesha 3 4 5 #" \
+			git rebase -i --root 2>actual &&
+			test_i18ngrep "edit XXXXXXX False commit" actual &&
+			test_i18ngrep "You can fix this with .git rebase --edit-todo.." \
+					actual &&
+		FAKE_LINES="1 2 4 5 6" git rebase --edit-todo
+	) &&
 	git rebase --continue &&
 	test E = $(git cat-file commit HEAD | sed -ne \$p)
 '
@@ -1419,42 +1701,105 @@ test_expect_success 'editor saves as CR/LF' '
 	)
 '
 
-SQ="'"
 test_expect_success 'rebase -i --gpg-sign=<key-id>' '
 	test_when_finished "test_might_fail git rebase --abort" &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1" git rebase -i --gpg-sign="\"S I Gner\"" HEAD^ \
-		>out 2>err &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1" git rebase -i --gpg-sign="\"S I Gner\"" \
+			HEAD^ >out 2>err
+	) &&
 	test_i18ngrep "$SQ-S\"S I Gner\"$SQ" err
 '
 
 test_expect_success 'rebase -i --gpg-sign=<key-id> overrides commit.gpgSign' '
 	test_when_finished "test_might_fail git rebase --abort" &&
 	test_config commit.gpgsign true &&
-	set_fake_editor &&
-	FAKE_LINES="edit 1" git rebase -i --gpg-sign="\"S I Gner\"" HEAD^ \
-		>out 2>err &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 1" git rebase -i --gpg-sign="\"S I Gner\"" \
+			HEAD^ >out 2>err
+	) &&
 	test_i18ngrep "$SQ-S\"S I Gner\"$SQ" err
 '
 
 test_expect_success 'valid author header after --root swap' '
 	rebase_setup_and_clean author-header no-conflict-branch &&
-	set_fake_editor &&
 	git commit --amend --author="Au ${SQ}thor <author@example.com>" --no-edit &&
 	git cat-file commit HEAD | grep ^author >expected &&
-	FAKE_LINES="5 1" git rebase -i --root &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="5 1" git rebase -i --root
+	) &&
 	git cat-file commit HEAD^ | grep ^author >actual &&
 	test_cmp expected actual
 '
 
 test_expect_success 'valid author header when author contains single quote' '
 	rebase_setup_and_clean author-header no-conflict-branch &&
-	set_fake_editor &&
 	git commit --amend --author="Au ${SQ}thor <author@example.com>" --no-edit &&
 	git cat-file commit HEAD | grep ^author >expected &&
-	FAKE_LINES="2" git rebase -i HEAD~2 &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="2" git rebase -i HEAD~2
+	) &&
 	git cat-file commit HEAD | grep ^author >actual &&
 	test_cmp expected actual
 '
 
+test_expect_success 'post-commit hook is called' '
+	test_when_finished "rm -f .git/hooks/post-commit" &&
+	>actual &&
+	mkdir -p .git/hooks &&
+	write_script .git/hooks/post-commit <<-\EOS &&
+	git rev-parse HEAD >>actual
+	EOS
+	(
+		set_fake_editor &&
+		FAKE_LINES="edit 4 1 reword 2 fixup 3" git rebase -i A E &&
+		echo x>file3 &&
+		git add file3 &&
+		FAKE_COMMIT_MESSAGE=edited git rebase --continue
+	) &&
+	git rev-parse HEAD@{5} HEAD@{4} HEAD@{3} HEAD@{2} HEAD@{1} HEAD \
+		>expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'correct error message for partial commit after empty pick' '
+	test_when_finished "git rebase --abort" &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="2 1 1" &&
+		export FAKE_LINES &&
+		test_must_fail git rebase -i A D
+	) &&
+	echo x >file1 &&
+	test_must_fail git commit file1 2>err &&
+	test_i18ngrep "cannot do a partial commit during a rebase." err
+'
+
+test_expect_success 'correct error message for commit --amend after empty pick' '
+	test_when_finished "git rebase --abort" &&
+	(
+		set_fake_editor &&
+		FAKE_LINES="1 1" &&
+		export FAKE_LINES &&
+		test_must_fail git rebase -i A D
+	) &&
+	echo x>file1 &&
+	test_must_fail git commit -a --amend 2>err &&
+	test_i18ngrep "middle of a rebase -- cannot amend." err
+'
+
+test_expect_success 'todo has correct onto hash' '
+	GIT_SEQUENCE_EDITOR=cat git rebase -i no-conflict-branch~4 no-conflict-branch >actual &&
+	onto=$(git rev-parse --short HEAD~4) &&
+	test_i18ngrep "^# Rebase ..* onto $onto" actual
+'
+
+# This must be the last test in this file
+test_expect_success '$EDITOR and friends are unchanged' '
+	test_editor_unchanged
+'
+
 test_done