rebase -i: handle fixup! fixup! in --autosquash

In rebase -i --autosquash, ignore all "fixup! " or "squash! " after the
first.  This supports the case when a git commit --fixup/--squash referred
to an earlier fixup/squash instead of the original commit (whether
intentionally, as when the user expressly meant to note that the commit
fixes an earlier fixup; or inadvertently, as when the user meant to refer to
the original commit with :/msg; or out of laziness, as when the user could
remember how to refer to the fixup but not the original).

In the todo list, the full commit message is preserved, in case it provides
useful cues to the user.  A test helper set_cat_todo_editor is introduced to
check this.

Helped-by: Thomas Rast <trast@inf.ethz.ch>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Andrew Pimlott <andrew@pimlott.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-rebase.txt

@@ -389,7 +389,9 @@ squash/fixup series.
 	the same ..., automatically modify the todo list of rebase -i
 	so that the commit marked for squashing comes right after the
 	commit to be modified, and change the action of the moved
-	commit from `pick` to `squash` (or `fixup`).
+	commit from `pick` to `squash` (or `fixup`).  Ignores subsequent
+	"fixup! " or "squash! " after the first, in case you referred to an
+	earlier fixup/squash with `git commit --fixup/--squash`.
 +
 This option is only valid when the '--interactive' option is used.
 +

git-rebase--interactive.sh

@@ -689,8 +689,22 @@ rearrange_squash () {
 		case "$message" in
 		"squash! "*|"fixup! "*)
 			action="${message%%!*}"
-			rest="${message#*! }"
-			echo "$sha1 $action $rest"
+			rest=$message
+			prefix=
+			# skip all squash! or fixup! (but save for later)
+			while :
+			do
+				case "$rest" in
+				"squash! "*|"fixup! "*)
+					prefix="$prefix${rest%%!*},"
+					rest="${rest#*! }"
+					;;
+				*)
+					break
+					;;
+				esac
+			done
+			echo "$sha1 $action $prefix $rest"
 			# if it's a single word, try to resolve to a full sha1 and
 			# emit a second copy. This allows us to match on both message
 			# and on sha1 prefix
@@ -699,7 +713,7 @@ rearrange_squash () {
 				if test -n "$fullsha"; then
 					# prefix the action to uniquely identify this line as
 					# intended for full sha1 match
-					echo "$sha1 +$action $fullsha"
+					echo "$sha1 +$action $prefix $fullsha"
 				fi
 			fi
 		esac
@@ -714,7 +728,7 @@ rearrange_squash () {
 		esac
 		printf '%s\n' "$pick $sha1 $message"
 		used="$used$sha1 "
-		while read -r squash action msg_content
+		while read -r squash action msg_prefix msg_content
 		do
 			case " $used" in
 			*" $squash "*) continue ;;
@@ -730,7 +744,8 @@ rearrange_squash () {
 				case "$message" in "$msg_content"*) emit=1;; esac ;;
 			esac
 			if test $emit = 1; then
-				printf '%s\n' "$action $squash $action! $msg_content"
+				real_prefix=$(echo "$msg_prefix" | sed "s/,/! /g")
+				printf '%s\n' "$action $squash ${real_prefix}$msg_content"
 				used="$used$squash "
 			fi
 		done <"$1.sq"

t/lib-rebase.sh

@@ -66,6 +66,20 @@ EOF
 	chmod a+x fake-editor.sh
 }
 
+# After set_cat_todo_editor, rebase -i will write the todo list (ignoring
+# blank lines and comments) to stdout, and exit failure (so you should run
+# it with test_must_fail).  This can be used to verify the expected user
+# experience, for todo list changes that do not affect the outcome of
+# rebase; or as an extra check in addition to checking the outcome.
+
+set_cat_todo_editor () {
+	write_script fake-editor.sh <<-\EOF
+	grep "^[^#]" "$1"
+	exit 1
+	EOF
+	test_set_editor "$(pwd)/fake-editor.sh"
+}
+
 # checks that the revisions in "$2" represent a linear range with the
 # subjects in "$1"
 test_linear_range () {

t/t3415-rebase-autosquash.sh

@@ -4,6 +4,8 @@ test_description='auto squash'
 
 . ./test-lib.sh
 
+. "$TEST_DIRECTORY"/lib-rebase.sh
+
 test_expect_success setup '
 	echo 0 >file0 &&
 	git add . &&
@@ -193,4 +195,59 @@ test_expect_success 'use commit --squash' '
 	test_auto_commit_flags squash 2
 '
 
+test_auto_fixup_fixup () {
+	git reset --hard base &&
+	echo 1 >file1 &&
+	git add -u &&
+	test_tick &&
+	git commit -m "$1! first" &&
+	echo 2 >file1 &&
+	git add -u &&
+	test_tick &&
+	git commit -m "$1! $2! first" &&
+	git tag "final-$1-$2" &&
+	test_tick &&
+	(
+		set_cat_todo_editor &&
+		test_must_fail git rebase --autosquash -i HEAD^^^^ >actual &&
+		cat >expected <<-EOF &&
+		pick $(git rev-parse --short HEAD^^^) first commit
+		$1 $(git rev-parse --short HEAD^) $1! first
+		$1 $(git rev-parse --short HEAD) $1! $2! first
+		pick $(git rev-parse --short HEAD^^) second commit
+		EOF
+		test_cmp expected actual
+	) &&
+	git rebase --autosquash -i HEAD^^^^ &&
+	git log --oneline >actual &&
+	test_line_count = 3 actual
+	git diff --exit-code "final-$1-$2" &&
+	test 2 = "$(git cat-file blob HEAD^:file1)" &&
+	if test "$1" = "fixup"
+	then
+		test 1 = $(git cat-file commit HEAD^ | grep first | wc -l)
+	elif test "$1" = "squash"
+	then
+		test 3 = $(git cat-file commit HEAD^ | grep first | wc -l)
+	else
+		false
+	fi
+}
+
+test_expect_success 'fixup! fixup!' '
+	test_auto_fixup_fixup fixup fixup
+'
+
+test_expect_success 'fixup! squash!' '
+	test_auto_fixup_fixup fixup squash
+'
+
+test_expect_success 'squash! squash!' '
+	test_auto_fixup_fixup squash squash
+'
+
+test_expect_success 'squash! fixup!' '
+	test_auto_fixup_fixup squash fixup
+'
+
 test_done