There are many filesystem related errors that can occur with
MariaBackup. These already outputed to stderr with a good description of
the error. Many of these are permission or resource (file descriptor)
limits where the assertion and resulting core crash doesn't offer
developers anything more than the log message. To the user, assertions
and core crashes come across as poor error handling.
As such we return an error and handle this all the way up the stack.
The InnoDB DATA DIRECTORY attribute is not implemented via
symbolic links but something similar, *.isl files that contain
the names of data files.
InnoDB failed to ignore the DATA DIRECTORY attribute even though
the server was started with --skip-symbolic-links.
Native ALTER TABLE in InnoDB will retain the DATA DIRECTORY attribute
of the table, no matter if the table will be rebuilt or not.
Generic ALTER TABLE (with ALGORITHM=COPY) as well as TRUNCATE TABLE
will discard the DATA DIRECTORY attribute.
All tests have been run with and without the ./mtr option
--mysqld=--skip-symbolic-links
and some tests that use the InnoDB DATA DIRECTORY attribute
have been adjusted for this.
