Only show the latest version in the Arch index

[ExplodingDragon]

Only show the latest version of the package in the arch repo.

closes #33534

[wxiaoguang]

Actually I have some questions about the design.

• KEEP_LATEST_VERSION sounds like "only keep the package with latest version, and delete others"
• After reading code, I think it means that "only show the package with latest version in the package index"

So the questions are:

• Should we delete the old packages? Or not delete, just hide them from the index (this PR does)?
• Could it ("deleting old packages" or "not-deleting but just hide old packages from index") be a general behavior for other package registries?
• The config name sounds misleading: I think it should clarify what's the expected result in the name: deleting, or just hiding.

[ExplodingDragon]

Actually I have some questions about the design.

* `KEEP_LATEST_VERSION` sounds like "only keep the package with latest version, and delete others"

* After reading code, I think it means that "only show the package with latest version in the package index"

So the questions are:

* Should we delete the old packages? Or not delete, just hide them from the index (this PR does)?

* Could it ("deleting old packages" or "not-deleting but just hide old packages from index") be a general behavior for other package registries?

* The config name sounds misleading: I think it should clarify what's the expected result in the name: deleting, or just hiding.

@wxiaoguang Sorry, I misspoke. KEEP_LATEST_VERSION will change to SHOW_LATEST_VERSION.

[wxiaoguang]

Are there some reference documents for the "only show latest version in index" behavior? (The question is why it is needed to be done on server side, since client could always figure out the latest version)

[ExplodingDragon]

Are there some reference documents for the "only show latest version in index" behavior? (The question is why it is needed to be done on server side, since client could always figure out the latest version)

@wxiaoguang No, this comes from my subjective opinion. Having too many packages will make the index larger, and most of the time, there isn't much demand for downloading older versions of software packages. Other package registries are facing the same situation.

Just like Arch Linux's rolling release model, which only keeps the latest version.

[wxiaoguang]

@KN4CK3R do you have more suggestions for this change?

[KN4CK3R]

services/packages/arch/vercmp.go

Not sure this is required. Just using the last uploaded package should be good (order by time of upload). This would also allow to revert back to older version by deleting and re-uploading old version.

I would go with that easy approach too because it will cover most (but sure, not all) use cases. To get the latest package version the SearchLatestVersions function can be used. But if you insist to replicate the full version comparison I will not block it.

[wxiaoguang]

To get the latest package version the SearchLatestVersions function can be used. But if you insist to replicate the full version comparison I will not block it.

@ExplodingDragon what do you think about it? Keep the current approach, or use SearchLatestVersions? If it replicates the version comparison, could there be some more comments about why not using SearchLatestVersions?

[ExplodingDragon]

what do you think about it? Keep the current approach, or use SearchLatestVersions?

@wxiaoguang I still believe that comparing the complete versions makes more sense.

Simply using the last uploaded version goes against intuition. Reverting to a previous version should involve deleting the new version, rather than uploading the old version to overwrite the index of the new one.

Just like Arch Wiki Downgrading packages said, randomly downgrading can mess up dependencies:

If a downgrade involves a soname change, all dependencies may need downgrading or rebuilding too.

---

Downgrading is a risky move and shouldn't be taken lightly or handled in a simplistic manner.

[KN4CK3R]

Simply using the last uploaded version goes against intuition. Reverting to a previous version should involve deleting the new version, rather than uploading the old version to overwrite the index of the new one.

That's not intended. As you said, you delete the new version which makes the previous version the newest. You don't upload an old version. Then the index contains the previous version again (which is now the new version). Therefore it's still not needed to parse every version to compare them.