Add usage info at migration script generator.

Also suppress error at the latest migration script
for backward compatibility with existing database, in which
open_invitations column wasn't added via migration.

pkg/database/migrate/20140310104446_add_open_invitation_column.go

@@ -9,10 +9,9 @@ func (r *rev20140310104446) Revision() int64 {
 }
 
 func (r *rev20140310104446) Up(mg *MigrationDriver) error {
-	if _, err := mg.AddColumn("settings", "open_invitations BOOLEAN"); err != nil {
+	// Suppress error here for backward compatibility
-		return err
+	_, err := mg.AddColumn("settings", "open_invitations BOOLEAN")
-	}
+	_, err = mg.Tx.Exec("UPDATE settings SET open_invitations=0 WHERE open_invitations IS NULL")
-	_, err := mg.Tx.Exec("UPDATE settings SET open_invitations=0 WHERE open_invitations IS NULL")
 	return err
 }
 

pkg/database/migrate/migration

@@ -9,6 +9,24 @@ titleize() {
     echo "$1" | sed -r -e "s/-|_/ /g" -e 's/\b(.)/\U\1/g' -e 's/ //g'
 }
 
+howto() {
+    echo "Usage:"
+    echo "    ./migration create_sample_table"
+    echo ""
+    echo "Above invocation will create a migration script called:"
+    echo "    ${REV}_create_sample_table.go"
+    echo "You can add your migration step at the Up and Down function"
+    echo "definition inside the file."
+    echo ""
+    echo "Database transaction available through MigrationDriver,"
+    echo "so you can access mg.Tx (sql.Tx instance) directly,"
+    echo "there are also some migration helpers available, see api.go"
+    echo "for the list of available helpers (Operation interface)."
+    echo ""
+}
+
+[[ $# -eq 0 ]] && howto && exit 0
+
 cat > ${REV}_$filename.go << EOF
 package migrate
 
@@ -20,11 +38,11 @@ func (r *rev$REV) Revision() int64 {
 ${TAB}return $REV
 }
 
-func (r *rev$REV) Up(op Operation) error {
+func (r *rev$REV) Up(mg *MigrationDriver) error {
 ${TAB}// Migration steps here
 }
 
-func (r *rev$REV) Down(op Operation) error {
+func (r *rev$REV) Down(mg *MigrationDriver) error {
 ${TAB}// Revert migration steps here
 }
 EOF