Add a command-line-only option to prevent overwriting the file specified
as external data file.
This option is only available on the qemu-img create command line, not
via blockdev-create, as it makes no sense there: That interface
separates file creation and formatting, so where the external data file
attached to a newly formatted qcow2 node comes from is completely up to
the user.
Implementation detail: Enabling this option will not only not overwrite
the external data file, but also assume it already exists, for two
reasons:
- It is simpler than checking whether the file exists, and only skipping
creating it when it does not. It is therefore also less error-prone,
i.e. we can never accidentally overwrite an existing file because we
made some mistake in checking whether it exists.
- I think it makes sense from a user's perspective: You set this option
when you want to use an existing data file, and you unset it when you
want a new one. Getting an error when you expect to use an existing
data file seems to me a nice warning that something is not right.
Signed-off-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20250530084448.192369-2-hreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[kwolf: Removed redundant has_data_file_raw check]
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
910451bc5b