rebase -i: call editor just once for a multi-squash

Sometimes you want to squash more than two commits.  Before this patch,
the editor was fired up for each squash command.  Now the editor is
started only with the last squash command.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-rebase--interactive.sh

@@ -19,6 +19,8 @@ require_work_tree
 DOTEST="$GIT_DIR/.dotest-merge"
 TODO="$DOTEST"/todo
 DONE="$DOTEST"/done
+MSG="$DOTEST"/message
+SQUASH_MSG="$DOTEST"/message-squash
 REWRITTEN="$DOTEST"/rewritten
 PRESERVE_MERGES=
 STRATEGY=
@@ -158,6 +160,38 @@ pick_one_preserving_merges () {
 	esac
 }
 
+nth_string () {
+	case "$1" in
+	*1[0-9]|*[04-9]) echo "$1"th;;
+	*1) echo "$1"st;;
+	*2) echo "$1"nd;;
+	*3) echo "$1"rd;;
+	esac
+}
+
+make_squash_message () {
+	if [ -f "$SQUASH_MSG" ]; then
+		COUNT=$(($(sed -n "s/^# This is [^0-9]*\([0-9]\+\).*/\1/p" \
+			< "$SQUASH_MSG" | tail -n 1)+1))
+		echo "# This is a combination of $COUNT commits."
+		sed -n "2,\$p" < "$SQUASH_MSG"
+	else
+		COUNT=2
+		echo "# This is a combination of two commits."
+		echo "# The first commit's message is:"
+		echo
+		git cat-file commit HEAD | sed -e '1,/^$/d'
+		echo
+	fi
+	echo "# This is the $(nth_string $COUNT) commit message:"
+	echo
+	git cat-file commit $1 | sed -e '1,/^$/d'
+}
+
+peek_next_command () {
+	sed -n "1s/ .*$//p" < "$TODO"
+}
+
 do_next () {
 	test -f "$DOTEST"/message && rm "$DOTEST"/message
 	test -f "$DOTEST"/author-script && rm "$DOTEST"/author-script
@@ -194,17 +228,19 @@ do_next () {
 			die "Cannot 'squash' without a previous commit"
 
 		mark_action_done
-		MSG="$DOTEST"/message
-		echo "# This is a combination of two commits." > "$MSG"
-		echo "# The first commit's message is:" >> "$MSG"
-		echo >> "$MSG"
-		git cat-file commit HEAD | sed -e '1,/^$/d' >> "$MSG"
-		echo >> "$MSG"
+		make_squash_message $sha1 > "$MSG"
+		case "$(peek_next_command)" in
+		squash)
+			EDIT_COMMIT=
+			cp "$MSG" "$SQUASH_MSG"
+		;;
+		*)
+			EDIT_COMMIT=-e
+			test -f "$SQUASH_MSG" && rm "$SQUASH_MSG"
+		esac
+
 		failed=f
 		pick_one -n $sha1 || failed=t
-		echo "# And this is the 2nd commit message:" >> "$MSG"
-		echo >> "$MSG"
-		git cat-file commit $sha1 | sed -e '1,/^$/d' >> "$MSG"
 		git reset --soft HEAD^
 		author_script=$(get_author_ident_from_commit $sha1)
 		echo "$author_script" > "$DOTEST"/author-script
@@ -213,7 +249,7 @@ do_next () {
 			# This is like --amend, but with a different message
 			eval "$author_script"
 			export GIT_AUTHOR_NAME GIT_AUTHOR_EMAIL GIT_AUTHOR_DATE
-			git commit -F "$MSG" -e
+			git commit -F "$MSG" $EDIT_COMMIT
 			;;
 		t)
 			cp "$MSG" "$GIT_DIR"/MERGE_MSG

t/t3404-rebase-interactive.sh

@@ -65,6 +65,7 @@ cat > fake-editor.sh << EOF
 #!/bin/sh
 test "\$1" = .git/COMMIT_EDITMSG && {
 	test -z "\$FAKE_COMMIT_MESSAGE" || echo "\$FAKE_COMMIT_MESSAGE" > "\$1"
+	test -z "\$FAKE_COMMIT_AMEND" || echo "\$FAKE_COMMIT_AMEND" >> "\$1"
 	exit
 }
 test -z "\$FAKE_LINES" && exit
@@ -212,4 +213,12 @@ test_expect_success 'verbose flag is heeded, even after --continue' '
 	grep "^ file1 |    2 +-$" output
 '
 
+test_expect_success 'multi-squash only fires up editor once' '
+	base=$(git rev-parse HEAD~4) &&
+	FAKE_COMMIT_AMEND="ONCE" FAKE_LINES="1 squash 2 squash 3 squash 4" \
+		git rebase -i $base &&
+	test $base = $(git rev-parse HEAD^) &&
+	test 1 = $(git show | grep ONCE | wc -l)
+'
+
 test_done