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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>