incusd/instances/publish: Fix base metadata

[stgraber]

Closes #1371

[Salamandar]

There actually is a bug that prevents the re-writing of metadata.yaml. We should not test for this and always rewrite the file:
stgraber@12b7b37#diff-33b72d6f2eb9bdf746e65cf613e9bf838ef1bafc1a576e2667c7ef4f7899de2cR5294

EDIT: The same test is performed to conditionnally add the file to the archive (well it conditions the offset and the second branch is buggy) and should be removed too:
stgraber@12b7b37#diff-33b72d6f2eb9bdf746e65cf613e9bf838ef1bafc1a576e2667c7ef4f7899de2cR5294

[Salamandar]

The whole if/else block could be replaced by :

	if util.PathExists(fnam) {
		logger.Errorf("metadata.yaml DID exist")
		// Parse the metadata.
		content, err := os.ReadFile(fnam)
		if err != nil {
			_ = tarWriter.Close()
			d.logger.Error("Failed exporting instance", ctxMap)
			return meta, err
		}

		err = yaml.Unmarshal(content, &meta)
		if err != nil {
			_ = tarWriter.Close()
			d.logger.Error("Failed exporting instance", ctxMap)
			return meta, err
		}

		// Fill in the metadata.
		meta.Architecture = arch
		meta.CreationDate = time.Now().UTC().Unix()
		if !expiration.IsZero() {
			meta.ExpiryDate = expiration.UTC().Unix()
		}
	}

	// Fill in the metadata.
	meta.Architecture = arch
	meta.CreationDate = time.Now().UTC().Unix()
	meta.Properties = properties
	if !expiration.IsZero() {
		meta.ExpiryDate = expiration.UTC().Unix()
	}

	// Generate a new metadata.yaml.
	tempDir, err := os.MkdirTemp("", "incus_metadata_")
	if err != nil {
		_ = tarWriter.Close()
		d.logger.Error("Failed exporting instance", ctxMap)
		return meta, err
	}

	defer func() { _ = os.RemoveAll(tempDir) }()

	data, err := yaml.Marshal(&meta)
	if err != nil {
		_ = tarWriter.Close()
		d.logger.Error("Failed exporting instance", ctxMap)
		return meta, err
	}

	// Write the actual file.
	fnam = filepath.Join(tempDir, "metadata.yaml")
	err = os.WriteFile(fnam, data, 0644)
	if err != nil {
		_ = tarWriter.Close()
		d.logger.Error("Failed exporting instance", ctxMap)
		return meta, err
	}

	// Include metadata.yaml in the tarball.
	fi, err := os.Lstat(fnam)
	if err != nil {
		_ = tarWriter.Close()
		d.logger.Debug("Error statting during export", logger.Ctx{"fileName": fnam})
		d.logger.Error("Failed exporting instance", ctxMap)
		return meta, err
	}

	tmpOffset := len(path.Dir(fnam)) + 1
	err = tarWriter.WriteFile(fnam[tmpOffset:], fnam, fi, false)
	if err != nil {
		_ = tarWriter.Close()
		d.logger.Debug("Error writing to tarfile", logger.Ctx{"err": err})
		d.logger.Error("Failed exporting instance", ctxMap)
		return meta, err
	}
	

That way we can ensure the creationDate, expiry, properties are all overwritten in all cases, as expected.

[stgraber]

We shouldn't rewrite the properties, priorities should only be generated if the metadata doesn't already exist as the user may have properly pre-created/updated the metadata through incus config metadata edit.

[Salamandar]

Alright, looks like the state of the current main branch fixes the issue. Thanks a lot ! <3