Merge branch 'en/pull-conflicting-options'

"git pull" had various corner cases that were not well thought out
around its --rebase backend, e.g. "git pull --ff-only" did not stop
but went ahead and rebased when the history on other side is not a
descendant of our history.  The series tries to fix them up.

* en/pull-conflicting-options:
  pull: fix handling of multiple heads
  pull: update docs & code for option compatibility with rebasing
  pull: abort by default when fast-forwarding is not possible
  pull: make --rebase and --no-rebase override pull.ff=only
  pull: since --ff-only overrides, handle it first
  pull: abort if --ff-only is given and fast-forwarding is impossible
  t7601: add tests of interactions with multiple merge heads and config
  t7601: test interaction of merge/rebase/fast-forward flags and options

11 files changed, 266 insertions, 62 deletions

diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index e561a8e485..28683d059d 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -65,7 +65,7 @@ test_expect_success setup '
 	export GIT_AUTHOR_DATE GIT_COMMITTER_DATE &&
 
 	git checkout master &&
-	git pull -s ours . side &&
+	git pull -s ours --no-rebase . side &&
 
 	GIT_AUTHOR_DATE="2006-06-26 00:05:00 +0000" &&
 	GIT_COMMITTER_DATE="2006-06-26 00:05:00 +0000" &&
diff --git a/t/t5520-pull.sh b/t/t5520-pull.sh
index e2c0c51022..672001a18b 100755
--- a/t/t5520-pull.sh
+++ b/t/t5520-pull.sh
@@ -136,12 +136,12 @@ test_expect_success 'the default remote . should not break explicit pull' '
 	git reset --hard HEAD^ &&
 	echo file >expect &&
 	test_cmp expect file &&
-	git pull . second &&
+	git pull --no-rebase . second &&
 	echo modified >expect &&
 	test_cmp expect file &&
 	git reflog -1 >reflog.actual &&
 	sed "s/^[0-9a-f][0-9a-f]*/OBJID/" reflog.actual >reflog.fuzzy &&
-	echo "OBJID HEAD@{0}: pull . second: Fast-forward" >reflog.expected &&
+	echo "OBJID HEAD@{0}: pull --no-rebase . second: Fast-forward" >reflog.expected &&
 	test_cmp reflog.expected reflog.fuzzy
 '
 
@@ -226,7 +226,7 @@ test_expect_success 'fail if the index has unresolved entries' '
 	test_commit modified2 file &&
 	git ls-files -u >unmerged &&
 	test_must_be_empty unmerged &&
-	test_must_fail git pull . second &&
+	test_must_fail git pull --no-rebase . second &&
 	git ls-files -u >unmerged &&
 	test_file_not_empty unmerged &&
 	cp file expected &&
@@ -409,37 +409,37 @@ test_expect_success 'pull --rebase --no-autostash & rebase.autostash unset' '
 
 test_expect_success 'pull succeeds with dirty working directory and merge.autostash set' '
 	test_config merge.autostash true &&
-	test_pull_autostash 2
+	test_pull_autostash 2 --no-rebase
 '
 
 test_expect_success 'pull --autostash & merge.autostash=true' '
 	test_config merge.autostash true &&
-	test_pull_autostash 2 --autostash
+	test_pull_autostash 2 --autostash --no-rebase
 '
 
 test_expect_success 'pull --autostash & merge.autostash=false' '
 	test_config merge.autostash false &&
-	test_pull_autostash 2 --autostash
+	test_pull_autostash 2 --autostash --no-rebase
 '
 
 test_expect_success 'pull --autostash & merge.autostash unset' '
 	test_unconfig merge.autostash &&
-	test_pull_autostash 2 --autostash
+	test_pull_autostash 2 --autostash --no-rebase
 '
 
 test_expect_success 'pull --no-autostash & merge.autostash=true' '
 	test_config merge.autostash true &&
-	test_pull_autostash_fail --no-autostash
+	test_pull_autostash_fail --no-autostash --no-rebase
 '
 
 test_expect_success 'pull --no-autostash & merge.autostash=false' '
 	test_config merge.autostash false &&
-	test_pull_autostash_fail --no-autostash
+	test_pull_autostash_fail --no-autostash --no-rebase
 '
 
 test_expect_success 'pull --no-autostash & merge.autostash unset' '
 	test_unconfig merge.autostash &&
-	test_pull_autostash_fail --no-autostash
+	test_pull_autostash_fail --no-autostash --no-rebase
 '
 
 test_expect_success 'pull.rebase' '
diff --git a/t/t5521-pull-options.sh b/t/t5521-pull-options.sh
index 63a688bdbf..7601c919fd 100755
--- a/t/t5521-pull-options.sh
+++ b/t/t5521-pull-options.sh
@@ -113,7 +113,7 @@ test_expect_success 'git pull --force' '
 	git pull two &&
 	test_commit A &&
 	git branch -f origin &&
-	git pull --all --force
+	git pull --no-rebase --all --force
 	)
 '
 
@@ -179,7 +179,7 @@ test_expect_success 'git pull --allow-unrelated-histories' '
 	(
 		cd dst &&
 		test_must_fail git pull ../src side &&
-		git pull --allow-unrelated-histories ../src side
+		git pull --no-rebase --allow-unrelated-histories ../src side
 	)
 '
 
diff --git a/t/t5524-pull-msg.sh b/t/t5524-pull-msg.sh
index c278adaa5a..b2be3605f5 100755
--- a/t/t5524-pull-msg.sh
+++ b/t/t5524-pull-msg.sh
@@ -28,7 +28,7 @@ test_expect_success setup '
 test_expect_success pull '
 (
 	cd cloned &&
-	git pull --log &&
+	git pull --no-rebase --log &&
 	git log -2 &&
 	git cat-file commit HEAD >result &&
 	grep Dollar result
@@ -41,7 +41,7 @@ test_expect_success '--log=1 limits shortlog length' '
 	git reset --hard HEAD^ &&
 	test "$(cat afile)" = original &&
 	test "$(cat bfile)" = added &&
-	git pull --log=1 &&
+	git pull --no-rebase --log=1 &&
 	git log -3 &&
 	git cat-file commit HEAD >result &&
 	grep Dollar result &&
diff --git a/t/t5553-set-upstream.sh b/t/t5553-set-upstream.sh
index b1d614ce18..9c12c0f8c3 100755
--- a/t/t5553-set-upstream.sh
+++ b/t/t5553-set-upstream.sh
@@ -108,27 +108,27 @@ test_expect_success 'setup commit on main and other pull' '
 
 test_expect_success 'pull --set-upstream upstream main sets branch main but not other' '
 	clear_config main other &&
-	git pull --set-upstream upstream main &&
+	git pull --no-rebase --set-upstream upstream main &&
 	check_config main upstream refs/heads/main &&
 	check_config_missing other
 '
 
 test_expect_success 'pull --set-upstream main:other2 does not set the branch other2' '
 	clear_config other2 &&
-	git pull --set-upstream upstream main:other2 &&
+	git pull --no-rebase --set-upstream upstream main:other2 &&
 	check_config_missing other2
 '
 
 test_expect_success 'pull --set-upstream upstream other sets branch main' '
 	clear_config main other &&
-	git pull --set-upstream upstream other &&
+	git pull --no-rebase --set-upstream upstream other &&
 	check_config main upstream refs/heads/other &&
 	check_config_missing other
 '
 
 test_expect_success 'pull --set-upstream upstream tag does not set the tag' '
 	clear_config three &&
-	git pull --tags --set-upstream upstream three &&
+	git pull --no-rebase --tags --set-upstream upstream three &&
 	check_config_missing three
 '
 
@@ -144,16 +144,16 @@ test_expect_success 'pull --set-upstream http://nosuchdomain.example.com fails w
 
 test_expect_success 'pull --set-upstream upstream HEAD sets branch HEAD' '
 	clear_config main other &&
-	git pull --set-upstream upstream HEAD &&
+	git pull --no-rebase --set-upstream upstream HEAD &&
 	check_config main upstream HEAD &&
 	git checkout other &&
-	git pull --set-upstream upstream HEAD &&
+	git pull --no-rebase --set-upstream upstream HEAD &&
 	check_config other upstream HEAD
 '
 
 test_expect_success 'pull --set-upstream upstream with more than one branch does nothing' '
 	clear_config main three &&
-	git pull --set-upstream upstream main three &&
+	git pull --no-rebase --set-upstream upstream main three &&
 	check_config_missing main &&
 	check_config_missing three
 '
diff --git a/t/t5604-clone-reference.sh b/t/t5604-clone-reference.sh
index e845d621f6..24340e6d56 100755
--- a/t/t5604-clone-reference.sh
+++ b/t/t5604-clone-reference.sh
@@ -87,7 +87,7 @@ test_expect_success 'updating origin' '
 '
 
 test_expect_success 'pulling changes from origin' '
-	git -C C pull origin
+	git -C C pull --no-rebase origin
 '
 
 # the 2 local objects are commit and tree from the merge
@@ -96,7 +96,7 @@ test_expect_success 'that alternate to origin gets used' '
 '
 
 test_expect_success 'pulling changes from origin' '
-	git -C D pull origin
+	git -C D pull --no-rebase origin
 '
 
 # the 5 local objects are expected; file3 blob, commit in A to add it
diff --git a/t/t6402-merge-rename.sh b/t/t6402-merge-rename.sh
index 3da2896e3b..3a32b1a45c 100755
--- a/t/t6402-merge-rename.sh
+++ b/t/t6402-merge-rename.sh
@@ -103,7 +103,7 @@ test_expect_success 'setup' '
 test_expect_success 'pull renaming branch into unrenaming one' \
 '
 	git show-branch &&
-	test_expect_code 1 git pull . white &&
+	test_expect_code 1 git pull --no-rebase . white &&
 	git ls-files -s &&
 	test_stdout_line_count = 3 git ls-files -u B &&
 	test_stdout_line_count = 1 git ls-files -s N &&
@@ -119,7 +119,7 @@ test_expect_success 'pull renaming branch into another renaming one' \
 	rm -f B &&
 	git reset --hard &&
 	git checkout red &&
-	test_expect_code 1 git pull . white &&
+	test_expect_code 1 git pull --no-rebase . white &&
 	test_stdout_line_count = 3 git ls-files -u B &&
 	test_stdout_line_count = 1 git ls-files -s N &&
 	sed -ne "/^g/{
@@ -133,7 +133,7 @@ test_expect_success 'pull unrenaming branch into renaming one' \
 '
 	git reset --hard &&
 	git show-branch &&
-	test_expect_code 1 git pull . main &&
+	test_expect_code 1 git pull --no-rebase . main &&
 	test_stdout_line_count = 3 git ls-files -u B &&
 	test_stdout_line_count = 1 git ls-files -s N &&
 	sed -ne "/^g/{
@@ -147,7 +147,7 @@ test_expect_success 'pull conflicting renames' \
 '
 	git reset --hard &&
 	git show-branch &&
-	test_expect_code 1 git pull . blue &&
+	test_expect_code 1 git pull --no-rebase . blue &&
 	test_stdout_line_count = 1 git ls-files -u A &&
 	test_stdout_line_count = 1 git ls-files -u B &&
 	test_stdout_line_count = 1 git ls-files -u C &&
@@ -163,7 +163,7 @@ test_expect_success 'interference with untracked working tree file' '
 	git reset --hard &&
 	git show-branch &&
 	echo >A this file should not matter &&
-	test_expect_code 1 git pull . white &&
+	test_expect_code 1 git pull --no-rebase . white &&
 	test_path_is_file A
 '
 
@@ -173,7 +173,7 @@ test_expect_success 'interference with untracked working tree file' '
 	git show-branch &&
 	rm -f A &&
 	echo >A this file should not matter &&
-	test_expect_code 1 git pull . red &&
+	test_expect_code 1 git pull --no-rebase . red &&
 	test_path_is_file A
 '
 
@@ -183,7 +183,7 @@ test_expect_success 'interference with untracked working tree file' '
 	git checkout -f main &&
 	git tag -f anchor &&
 	git show-branch &&
-	git pull . yellow &&
+	git pull --no-rebase . yellow &&
 	test_path_is_missing M &&
 	git reset --hard anchor
 '
@@ -210,7 +210,7 @@ test_expect_success 'updated working tree file should prevent the merge' '
 	echo >>M one line addition &&
 	cat M >M.saved &&
 	git update-index M &&
-	test_expect_code 128 git pull . yellow &&
+	test_expect_code 128 git pull --no-rebase . yellow &&
 	test_cmp M M.saved &&
 	rm -f M.saved
 '
@@ -222,7 +222,7 @@ test_expect_success 'interference with untracked working tree file' '
 	git tag -f anchor &&
 	git show-branch &&
 	echo >M this file should not matter &&
-	git pull . main &&
+	git pull --no-rebase . main &&
 	test_path_is_file M &&
 	! {
 		git ls-files -s |
diff --git a/t/t6409-merge-subtree.sh b/t/t6409-merge-subtree.sh
index d406b2343c..ba7890ec52 100755
--- a/t/t6409-merge-subtree.sh
+++ b/t/t6409-merge-subtree.sh
@@ -100,7 +100,7 @@ test_expect_success 'merge update' '
 	git checkout -b topic_2 &&
 	git commit -m "update git-gui" &&
 	cd ../git &&
-	git pull -s subtree gui topic_2 &&
+	git pull --no-rebase -s subtree gui topic_2 &&
 	git ls-files -s >actual &&
 	(
 		echo "100644 $o3 0	git-gui/git-gui.sh" &&
@@ -129,7 +129,7 @@ test_expect_success 'initial ambiguous subtree' '
 test_expect_success 'merge using explicit' '
 	cd ../git &&
 	git reset --hard topic_2 &&
-	git pull -Xsubtree=git-gui gui topic_2 &&
+	git pull --no-rebase -Xsubtree=git-gui gui topic_2 &&
 	git ls-files -s >actual &&
 	(
 		echo "100644 $o3 0	git-gui/git-gui.sh" &&
@@ -142,7 +142,7 @@ test_expect_success 'merge using explicit' '
 test_expect_success 'merge2 using explicit' '
 	cd ../git &&
 	git reset --hard topic_2 &&
-	git pull -Xsubtree=git-gui2 gui topic_2 &&
+	git pull --no-rebase -Xsubtree=git-gui2 gui topic_2 &&
 	git ls-files -s >actual &&
 	(
 		echo "100644 $o1 0	git-gui/git-gui.sh" &&
diff --git a/t/t6417-merge-ours-theirs.sh b/t/t6417-merge-ours-theirs.sh
index ac9aee9a66..ec065d6a65 100755
--- a/t/t6417-merge-ours-theirs.sh
+++ b/t/t6417-merge-ours-theirs.sh
@@ -69,11 +69,11 @@ test_expect_success 'binary file with -Xours/-Xtheirs' '
 '
 
 test_expect_success 'pull passes -X to underlying merge' '
-	git reset --hard main && git pull -s recursive -Xours . side &&
-	git reset --hard main && git pull -s recursive -X ours . side &&
-	git reset --hard main && git pull -s recursive -Xtheirs . side &&
-	git reset --hard main && git pull -s recursive -X theirs . side &&
-	git reset --hard main && test_must_fail git pull -s recursive -X bork . side
+	git reset --hard main && git pull --no-rebase -s recursive -Xours . side &&
+	git reset --hard main && git pull --no-rebase -s recursive -X ours . side &&
+	git reset --hard main && git pull --no-rebase -s recursive -Xtheirs . side &&
+	git reset --hard main && git pull --no-rebase -s recursive -X theirs . side &&
+	git reset --hard main && test_must_fail git pull --no-rebase -s recursive -X bork . side
 '
 
 test_expect_success SYMLINKS 'symlink with -Xours/-Xtheirs' '
diff --git a/t/t7601-merge-pull-config.sh b/t/t7601-merge-pull-config.sh
index 52e8ccc933..1f652f433e 100755
--- a/t/t7601-merge-pull-config.sh
+++ b/t/t7601-merge-pull-config.sh
@@ -27,120 +27,324 @@ test_expect_success 'setup' '
 	git tag c3
 '
 
-test_expect_success 'pull.rebase not set' '
+test_expect_success 'pull.rebase not set, ff possible' '
 	git reset --hard c0 &&
 	git pull . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and pull.ff=true' '
 	git reset --hard c0 &&
 	test_config pull.ff true &&
 	git pull . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and pull.ff=false' '
 	git reset --hard c0 &&
 	test_config pull.ff false &&
 	git pull . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and pull.ff=only' '
 	git reset --hard c0 &&
 	test_config pull.ff only &&
 	git pull . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --rebase given' '
 	git reset --hard c0 &&
 	git pull --rebase . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --no-rebase given' '
 	git reset --hard c0 &&
 	git pull --no-rebase . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --ff given' '
 	git reset --hard c0 &&
 	git pull --ff . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --no-ff given' '
 	git reset --hard c0 &&
 	git pull --no-ff . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --ff-only given' '
 	git reset --hard c0 &&
 	git pull --ff-only . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set (not-fast-forward)' '
 	git reset --hard c2 &&
-	git -c color.advice=always pull . c1 2>err &&
+	test_must_fail git -c color.advice=always pull . c1 2>err &&
 	test_decode_color <err >decoded &&
 	test_i18ngrep "<YELLOW>hint: " decoded &&
-	test_i18ngrep "Pulling without specifying how to reconcile" decoded
+	test_i18ngrep "You have divergent branches" decoded
 '
 
 test_expect_success 'pull.rebase not set and pull.ff=true (not-fast-forward)' '
 	git reset --hard c2 &&
 	test_config pull.ff true &&
 	git pull . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and pull.ff=false (not-fast-forward)' '
 	git reset --hard c2 &&
 	test_config pull.ff false &&
 	git pull . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and pull.ff=only (not-fast-forward)' '
 	git reset --hard c2 &&
 	test_config pull.ff only &&
 	test_must_fail git pull . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --rebase given (not-fast-forward)' '
 	git reset --hard c2 &&
 	git pull --rebase . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --no-rebase given (not-fast-forward)' '
 	git reset --hard c2 &&
 	git pull --no-rebase . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --ff given (not-fast-forward)' '
 	git reset --hard c2 &&
 	git pull --ff . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --no-ff given (not-fast-forward)' '
 	git reset --hard c2 &&
 	git pull --no-ff . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
 '
 
 test_expect_success 'pull.rebase not set and --ff-only given (not-fast-forward)' '
 	git reset --hard c2 &&
 	test_must_fail git pull --ff-only . c1 2>err &&
-	test_i18ngrep ! "Pulling without specifying how to reconcile" err
+	test_i18ngrep ! "You have divergent branches" err
+'
+
+test_does_rebase () {
+	git reset --hard c2 &&
+	git "$@" . c1 &&
+	# Check that we actually did a rebase
+	git rev-list --count HEAD >actual &&
+	git rev-list --merges --count HEAD >>actual &&
+	test_write_lines 3 0 >expect &&
+	test_cmp expect actual &&
+	rm actual expect
+}
+
+# Prefers merge over fast-forward
+test_does_merge_when_ff_possible () {
+	git reset --hard c0 &&
+	git "$@" . c1 &&
+	# Check that we actually did a merge
+	git rev-list --count HEAD >actual &&
+	git rev-list --merges --count HEAD >>actual &&
+	test_write_lines 3 1 >expect &&
+	test_cmp expect actual &&
+	rm actual expect
+}
+
+# Prefers fast-forward over merge or rebase
+test_does_fast_forward () {
+	git reset --hard c0 &&
+	git "$@" . c1 &&
+
+	# Check that we did not get any merges
+	git rev-list --count HEAD >actual &&
+	git rev-list --merges --count HEAD >>actual &&
+	test_write_lines 2 0 >expect &&
+	test_cmp expect actual &&
+
+	# Check that we ended up at c1
+	git rev-parse HEAD >actual &&
+	git rev-parse c1^{commit} >expect &&
+	test_cmp actual expect &&
+
+	# Remove temporary files
+	rm actual expect
+}
+
+# Doesn't fail when fast-forward not possible; does a merge
+test_falls_back_to_full_merge () {
+	git reset --hard c2 &&
+	git "$@" . c1 &&
+	# Check that we actually did a merge
+	git rev-list --count HEAD >actual &&
+	git rev-list --merges --count HEAD >>actual &&
+	test_write_lines 4 1 >expect &&
+	test_cmp expect actual &&
+	rm actual expect
+}
+
+# Attempts fast forward, which is impossible, and bails
+test_attempts_fast_forward () {
+	git reset --hard c2 &&
+	test_must_fail git "$@" . c1 2>err &&
+	test_i18ngrep "Not possible to fast-forward, aborting" err
+}
+
+#
+# Group 1: Interaction of --ff-only with --[no-]rebase
+# (And related interaction of pull.ff=only with pull.rebase)
+#
+test_expect_success '--ff-only overrides --rebase' '
+	test_attempts_fast_forward pull --rebase --ff-only
+'
+
+test_expect_success '--ff-only overrides --rebase even if first' '
+	test_attempts_fast_forward pull --ff-only --rebase
+'
+
+test_expect_success '--ff-only overrides --no-rebase' '
+	test_attempts_fast_forward pull --ff-only --no-rebase
+'
+
+test_expect_success 'pull.ff=only overrides pull.rebase=true' '
+	test_attempts_fast_forward -c pull.ff=only -c pull.rebase=true pull
+'
+
+test_expect_success 'pull.ff=only overrides pull.rebase=false' '
+	test_attempts_fast_forward -c pull.ff=only -c pull.rebase=false pull
+'
+
+# Group 2: --rebase=[!false] overrides --no-ff and --ff
+# (And related interaction of pull.rebase=!false and pull.ff=!only)
+test_expect_success '--rebase overrides --no-ff' '
+	test_does_rebase pull --rebase --no-ff
+'
+
+test_expect_success '--rebase overrides --ff' '
+	test_does_rebase pull --rebase --ff
+'
+
+test_expect_success '--rebase fast-forwards when possible' '
+	test_does_fast_forward pull --rebase --ff
+'
+
+test_expect_success 'pull.rebase=true overrides pull.ff=false' '
+	test_does_rebase -c pull.rebase=true -c pull.ff=false pull
+'
+
+test_expect_success 'pull.rebase=true overrides pull.ff=true' '
+	test_does_rebase -c pull.rebase=true -c pull.ff=true pull
+'
+
+# Group 3: command line flags take precedence over config
+test_expect_success '--ff-only takes precedence over pull.rebase=true' '
+	test_attempts_fast_forward -c pull.rebase=true pull --ff-only
+'
+
+test_expect_success '--ff-only takes precedence over pull.rebase=false' '
+	test_attempts_fast_forward -c pull.rebase=false pull --ff-only
+'
+
+test_expect_success '--no-rebase takes precedence over pull.ff=only' '
+	test_falls_back_to_full_merge -c pull.ff=only pull --no-rebase
+'
+
+test_expect_success '--rebase takes precedence over pull.ff=only' '
+	test_does_rebase -c pull.ff=only pull --rebase
+'
+
+test_expect_success '--rebase overrides pull.ff=true' '
+	test_does_rebase -c pull.ff=true pull --rebase
+'
+
+test_expect_success '--rebase overrides pull.ff=false' '
+	test_does_rebase -c pull.ff=false pull --rebase
+'
+
+test_expect_success '--rebase overrides pull.ff unset' '
+	test_does_rebase pull --rebase
+'
+
+# Group 4: --no-rebase heeds pull.ff=!only or explict --ff or --no-ff
+
+test_expect_success '--no-rebase works with --no-ff' '
+	test_does_merge_when_ff_possible pull --no-rebase --no-ff
+'
+
+test_expect_success '--no-rebase works with --ff' '
+	test_does_fast_forward pull --no-rebase --ff
+'
+
+test_expect_success '--no-rebase does ff if pull.ff unset' '
+	test_does_fast_forward pull --no-rebase
+'
+
+test_expect_success '--no-rebase heeds pull.ff=true' '
+	test_does_fast_forward -c pull.ff=true pull --no-rebase
+'
+
+test_expect_success '--no-rebase heeds pull.ff=false' '
+	test_does_merge_when_ff_possible -c pull.ff=false pull --no-rebase
+'
+
+# Group 5: pull.rebase=!false in combination with --no-ff or --ff
+test_expect_success 'pull.rebase=true and --no-ff' '
+	test_does_rebase -c pull.rebase=true pull --no-ff
+'
+
+test_expect_success 'pull.rebase=true and --ff' '
+	test_does_rebase -c pull.rebase=true pull --ff
+'
+
+test_expect_success 'pull.rebase=false and --no-ff' '
+	test_does_merge_when_ff_possible -c pull.rebase=false pull --no-ff
+'
+
+test_expect_success 'pull.rebase=false and --ff, ff possible' '
+	test_does_fast_forward -c pull.rebase=false pull --ff
+'
+
+test_expect_success 'pull.rebase=false and --ff, ff not possible' '
+	test_falls_back_to_full_merge -c pull.rebase=false pull --ff
+'
+
+# End of groupings for conflicting merge vs. rebase flags/options
+
+test_expect_success 'Multiple heads warns about inability to fast forward' '
+	git reset --hard c1 &&
+	test_must_fail git pull . c2 c3 2>err &&
+	test_i18ngrep "You have divergent branches" err
+'
+
+test_expect_success 'Multiple can never be fast forwarded' '
+	git reset --hard c0 &&
+	test_must_fail git -c pull.ff=only pull . c1 c2 c3 2>err &&
+	test_i18ngrep ! "You have divergent branches" err &&
+	# In addition to calling out "cannot fast-forward", we very much
+	# want the "multiple branches" piece to be called out to users.
+	test_i18ngrep "Cannot fast-forward to multiple branches" err
+'
+
+test_expect_success 'Cannot rebase with multiple heads' '
+	git reset --hard c0 &&
+	test_must_fail git -c pull.rebase=true pull . c1 c2 c3 2>err &&
+	test_i18ngrep ! "You have divergent branches" err &&
+	test_i18ngrep "Cannot rebase onto multiple branches." err
 '
 
 test_expect_success 'merge c1 with c2' '
diff --git a/t/t7603-merge-reduce-heads.sh b/t/t7603-merge-reduce-heads.sh
index 98948955ae..27cd94ad6f 100755
--- a/t/t7603-merge-reduce-heads.sh
+++ b/t/t7603-merge-reduce-heads.sh
@@ -68,7 +68,7 @@ test_expect_success 'merge c1 with c2, c3, c4, c5' '
 
 test_expect_success 'pull c2, c3, c4, c5 into c1' '
 	git reset --hard c1 &&
-	git pull . c2 c3 c4 c5 &&
+	git pull --no-rebase . c2 c3 c4 c5 &&
 	test "$(git rev-parse c1)" != "$(git rev-parse HEAD)" &&
 	test "$(git rev-parse c1)" = "$(git rev-parse HEAD^1)" &&
 	test "$(git rev-parse c2)" = "$(git rev-parse HEAD^2)" &&