storage: enable partial images by default

by default enable pulling a partial image, it is still possible to
disable the feature through the configuration file.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

docs/containers-storage.conf.5.md

@@ -84,7 +84,7 @@ The `storage.options` table supports the following options:
 **additionalimagestores**=[]
   Paths to additional container image stores. Usually these are read/only and stored on remote network shares.
 
-**pull_options** = {enable_partial_images = "false", use_hard_links = "false", ostree_repos=""}
+**pull_options** = {enable_partial_images = "true", use_hard_links = "false", ostree_repos=""}
 
 Allows specification of how storage is populated when pulling images. This
 option can speed the pulling process of images compressed with format zstd:chunked. Containers/storage looks

pkg/chunked/storage_linux.go

@@ -1701,7 +1701,7 @@ func (c *chunkedDiffer) ApplyDiff(dest string, options *archive.TarOptions, diff
 		UncompressedDigest: uncompressedDigest,
 	}
 
-	if !parseBooleanPullOption(c.storeOpts, "enable_partial_images", false) {
+	if !parseBooleanPullOption(c.storeOpts, "enable_partial_images", true) {
 		return output, errors.New("enable_partial_images not configured")
 	}
 

storage.conf

@@ -70,7 +70,7 @@ additionalimagestores = [
 #     Tells containers/storage where an ostree repository exists that might have
 #     previously pulled content which can be used when attempting to avoid
 #     pulling content from the container registry
-pull_options = {enable_partial_images = "false", use_hard_links = "false", ostree_repos=""}
+pull_options = {enable_partial_images = "true", use_hard_links = "false", ostree_repos=""}
 
 # Remap-UIDs/GIDs is the mapping from UIDs/GIDs as they should appear inside of
 # a container, to the UIDs/GIDs as they should appear outside of the container,