internal/tool: add templates for liquibase compatible migration files

internal/tool/tool.go

@@ -14,6 +14,7 @@ import (
 var (
 	// funcs contains the template.FuncMap for the different formatters.
 	funcs = template.FuncMap{
+		"inc": func(x int) int { return x + 1 },
 		// now format the current time in a lexicographically ascending order while maintaining human readability.
 		"now": func() string { return time.Now().Format("20060102150405") },
 		"rev": reverse,
@@ -51,6 +52,22 @@ func NewFlywayFormatter() (migrate.Formatter, error) {
 	)
 }
 
+// NewLiquibaseFormatter returns a migrate.Formatter computable with Liquibase.
+func NewLiquibaseFormatter() (migrate.Formatter, error) { // TODO(masseelch): add dbms property (meta data needed)
+	return templateFormatter(
+		"{{ now }}{{ with .Name }}_{{ . }}{{ end }}.sql",
+		`{{- $now := now -}}
+--liquibase formatted sql
+
+{{- range $index, $change := .Changes }}
+--changeset atlas:{{ $now }}-{{ inc $index }}
+{{ with $change.Comment }}--comment: {{ . }}{{ end }}
+{{ $change.Cmd }};
+{{ with $change.Reverse }}--rollback: {{ . }};{{ end }}
+{{ end }}`,
+	)
+}
+
 // templateFormatter parses the given templates and passes them on to the migrate.NewTemplateFormatter.
 func templateFormatter(templates ...string) (fmt migrate.Formatter, err error) {
 	tpls := make([]*template.Template, len(templates))

internal/tool/tool_test.go

@@ -5,6 +5,7 @@
 package tool_test
 
 import (
+	"fmt"
 	"io/fs"
 	"testing"
 	"time"
@@ -80,6 +81,23 @@ DROP TABLE t1 IF EXISTS;
 `,
 			},
 		},
+		{
+			"liquibase",
+			tool.NewLiquibaseFormatter,
+			map[string]string{
+				v + "_tooling-plan.sql": fmt.Sprintf(`--liquibase formatted sql
+--changeset atlas:%s-1
+--comment: create table t1
+CREATE TABLE t1(c int);
+--rollback: DROP TABLE t1 IF EXISTS;
+
+--changeset atlas:%s-2
+--comment: create table t2
+CREATE TABLE t2(c int);
+--rollback: DROP TABLE t2;
+`, v, v),
+			},
+		},
 	} {
 		t.Run(tt.name, func(t *testing.T) {
 			d := dir(t)