Rename `ErrSkipDesc` to `SkipNode`

[Shiwei Zhang]

#631 exports errSkipDesc to ErrSkipDesc so that copy can be skipped for mounting. However, ErrSkipDesc is not a real error that should be returned by any function.

I have looked into the golang built-in package io/fs and found SkipAll and SkipDir. To have consistent naming as the build-in packages, I propose that we should rename ErrSkipDesc to SkipDesc SkipNode (as discussed in comment section).

var SkipAll = errors.New("skip everything and stop the walk")
var SkipDir = errors.New("skip this directory")

@Wwwsylvia @ktarplee Any comments?

[Kyle Tarplee]

@shizhMSFT I do like the name SkipDesc better than ErrSkipDesc but maybe the abbreviation needs to be dropped as well. So I actually prefer SkipDescriptor for clarity.

[Shiwei Zhang]

SkipDescriptor sounds good to me.

[Kyle Tarplee]

Maybe SkipNode is a better name since we are actually skipping the node described by the descriptor and not the descriptor itself.

[Sajay Antony]

For API choices it always easier when we look at it in the context of code. Can we write up a small code block that would use SkipNode or skipDescriptor?

[Kyle Tarplee]

For API choices it always easier when we look at it in the context of code. Can we write up a small code block that would use SkipNode or skipDescriptor?

You see a use of ErrSkipDesc in #632

[Shiwei Zhang]

The name SkipNode sound more reasonable to me as we are copying graphs.

[Lixia (Sylvia) Lei]

SkipNode sounds good to me.