validate: remove autodetect for type and add require limit

[Mashimiao]

1. spec says any extra fields in json file can be ignored, so I think
   we can't clearly distingish which type the text file is, we'd better remove
   autodetect for text files.
2. without audotdetect, we must requrie to user to set file type for validation

Signed-off-by: Ma Shimiao [email protected]

[Mashimiao]

@opencontainers/image-tools-maintainers PTAL

[Mashimiao]

ping @coolljt0725 @xiekeyang @q384566678 @stevvooe

[zhouhao3]

I think in create and unpack also need to make the appropriate changes.

[Mashimiao]

create and unpack doesn't have text file type autodetect problem. Currently, whether type is required or not does not break their function. Let's solve validate's problem first. Then if necessary, we can make unified changes in another PR.

[zhouhao3]

LGTM

This can also solve the problem in #62 . Wait for other's opinion.

[coolljt0725]

Can we set a default type if --type is unset? It seems odd if it doesn't work without any options.

[Mashimiao]

I don't think it's a good idea. Because --type is a little special, it's a must be required option but there is not a value could be used for all files, that means it's almost impossible to find a suitable default value.
So, I think let it to be unset will be better.

[coolljt0725]

there is not a value could be used for all files, that means it's almost impossible to find a suitable default value.

Default is not a value for all files, it's value are most common. From that I know, it's not a good design from user perspective if a cli requires a option .

And I tested the patch

lei@ubuntu:~/images$ oci-image-tool validate busybox/
--type must be set
lei@ubuntu:~/images$ oci-image-tool validate --type imageLayout busybox/
1 errors detected:
busybox/: type "imageLayout" unimplemented
lei@ubuntu:~/images$ oci-image-tool validate --type image busybox/
autodetected image file type is: imageLayout
oci-image-tool: reference "latest": OK
busybox/: OK
Validation succeeded

Is the output autodetected image file type is: imageLayout necessary and why use --type imageLayout doesn't work but the autodetected image type is imageLayout?`

[Mashimiao]

Oh, sorry.... that's my fault. I should remove imageLayout from help and manpage.
In my design, users can only specify image,manifest,imageIndex,config to --type.
If we get that users want to validate an image, then we try to detect its type, may be a layout, tar file or zip file.
As you mentioned at #141 (comment), I try to use imageType to handle all image format.

[Mashimiao]

Updated, removed imageLayout. PTAL

[zhouhao3]

Also need to fix completions/bash/oci-image-tool.

[Mashimiao]

updated

[zhouhao3]

In general I agree this PR. @coolljt0725, WDYT?

[Mashimiao]

@opencontainers/image-tools-maintainers PTAL

[zhouhao3]

LGTM

ping @coolljt0725 @xiekeyang PTAL

[zhouhao3]

ping @coolljt0725 @xiekeyang

[Mashimiao]

ping @coolljt0725

[coolljt0725]

ping @opencontainers/image-tools-maintainers @wking PTAL. I'm not quite sure about this.

[zhouhao3]

ping @opencontainers/image-tools-maintainers

[Mashimiao]

@opencontainers/image-tools-maintainers PTAL

[vbatts]

@Mashimiao is the autodetect causing issues? I'm am all for reducing magic-detection, but if this is not causing issues, then what is the issue?

[Mashimiao]

Autodetect really causes issue. But I think that happens just when we use it for text file detection.
If we specified to validate the whole image not image files, it can easily and clearly find out the type of image. If the image is a directory, it must be a imageLayout. If not a directory, we can find out it content type and call validation function for that type.
So, I just removed the autodetec for image files(like index, config files), but retain the autodetect for image type.

[Mashimiao]

ping @vbatts

[stevvooe]

An image isn't the layout. The layout is the collection of resources that can make up an image. For example, I can still have an image and not have a layout.

[Mashimiao]

Yeah, agree. And as you said, layout makes up an image. If we have a layout then we have an image. The point is image may be stored in different file types.
But if you don't have a layout, then it will not be a valid OCI image.
So, how do you think we should change the help info?

[zhouhao3]

LGTM