backUp method
Backs up files (paths in the project; missing ones are noted as
missing, so a rollback deletes what the change created). A symbolic
link is backed up as a link, and the file it leads to too — what a
write through it changes. Throws a FileSystemException, backing up
nothing more, for a path that leads outside the project.
Implementation
void backUp(List<String> files) {
_checkOpen();
try {
for (final rel in files) {
final key = _inside(rel);
if (FileSystemEntity.isLinkSync(project.path(key))) {
_backUpLink(key);
_backUpFile(_landing(rel));
} else {
_backUpFile(key);
}
}
} finally {
_save();
}
}