[rewrite] Do not leave .zs-old files around

[probonopd]

When the file was already 100% downloaded and up to date and the user then tries to update it, a .zs-old file is left behind:

me@host:~$ ls
appimaged-x86_64.AppImage     Desktop    Downloads  Pictures
appimaged-x86_64.AppImage.zs-old  Documents  Music  Videos
me@host:~$ rm appimaged-x86_64.AppImage.zs-old 
me@host:~$ ls
appimaged-x86_64.AppImage  Desktop  Documents  Downloads  Music  Pictures  Videos
me@host:~$ Downloads/appimageupdate-x86_64.AppImage appimaged-x86_64.AppImage
Starting update...
Updating from generic server via ZSync
Update URL: https://github.com/AppImage/AppImageKit/releases/download/continuous/appimaged-x86_64.AppImage.zsync
zsync2: appimaged-x86_64.AppImage found, using as seed file
zsync2: Reading seed file: appimaged-x86_64.AppImage
zsync2: Usable data from seed files: 100.000000%
zsync2: Renaming temp file
zsync2: Fetching remaining blocks
zsync2: Verifying downloaded file
zsync2: checksum matches OK
zsync2: used 245760 local, fetched 0
100% done...
Update successful!
me@host:~$ ls
appimaged-x86_64.AppImage     Desktop    Downloads  Pictures
appimaged-x86_64.AppImage.zs-old  Documents  Music  Videos

[TheAssassin]

Rewrite does cleanup its backup files as of https://github.com/AppImage/AppImageUpdate/commit/4b1e3a3e7b50128e47af55cb2bf99d2c6fa061b7.

[probonopd]

Still an issue if you already have the new version downloaded. https://github.com/AppImage/AppImageUpdate/issues/36

[TheAssassin]

That issue originates from your idea to keep the old files and create a new one with the new filename. When there's a file called like the new filename, it will be backed up to avoid deleting it.

A "fix" for this would probably be to make the update check look whether there's such a new file, and whether it is equal to the server file. This avoids unnecessary updates.

[probonopd]

Just having two identical filenames does not mean that the content is necessarily the same. If your proposal takes this into account, then I am all for it.

[TheAssassin]

The idea is to apply the selected update check to this file, too, yes.

[TheAssassin]

This has probably been resolved since AppImageUpdate checks for updates before starting an actual update now. Please confirm.

[probonopd]

Did not encounter it recently, hence closing. Should reopen if the problem appears again. Thanks.

[probonopd]

AppImageUpdate-382-b61bee3-x86_64.AppImage still leaves around .zs-old files.

Let's do some check before exiting to clean up any remaining .zs-old files.

[TheAssassin]

That issue originates from your idea to keep the old files and create a new one with the new filename. When there's a file called like the new filename, it will be backed up to avoid deleting it.

[probonopd]

In the end, please let's make sure that no zs-old files are around anymore in any circumstance. Whatever happens.

[TheAssassin]

i don't intend to delete files with the same filename during updates. Tell the upstream to either do proper versioning and put the version number in the new file's filename.

Quoting you:

Just having two identical filenames does not mean that the content is necessarily the same. If your proposal takes this into account, then I am all for it.

[probonopd]

I have the following use case quite frequently:

Same application version, newer AppImage packaging.

[probonopd]

zs-old screams "error", "bug" at me.

[TheAssassin]

That's nothing we could fix. .zs-old just tells "previous file", not "error".

[probonopd]

Why can't it then just append ".old" to the original filename, or something like that. I really dislike that "zs" thing. Our users don't know (and should not have to know) anything about "zs".

[TheAssassin]

Because that extension is coming from zsync2, which retains compatibility with zsync.

[probonopd]

I know, but AppImageUpdate could should "catch" these files imho.

[probonopd]

By the way:

i don't intend to delete files with the same filename during updates. Tell the upstream to either do proper versioning and put the version number in the new file's filename.

We should think about this.

Just having two identical filenames does not mean that the content is necessarily the same.

That is correct.

But what is the intended behavior when running AppImageUpdate?

In my opinion, if everything goes well, there should be a new file with the new filename as specified by the author of the zsnyc file. If that is a new filename (e.g., with a new version number) then this file should be there in addition to the original file.

But if this is not a new filename (but rather an existing filename), shouldn't we overwrite the existing file with the new file (after we know the update was successful) and not leave an old file around? After all that seems to be what was wanted by the zsync file author.

Not 100% on what's the best thing to do here.

[TheAssassin]

I know, but AppImageUpdate could should "catch" these files imho.

How?

But if this is not a new filename (but rather an existing filename), shouldn't we overwrite the existing file with the new file (after we know the update was successful) and not leave an old file around?

Back when we developed this, you were a fan of keeping the old files around. If the new version doesn't work, you can still use the old AppImage...

After all that seems to be what was wanted by the zsync file author.

Not necessarily. And I don't think they should get that much control.

[probonopd]

Back when we developed this, you were a fan of keeping the old files around. If the new version doesn't work, you can still use the old AppImage...

True. I was thinking about files with a new name though.

Not 100% on what's the best thing to do here.

Still holds ;-)

[TheAssassin]

I don't think this is really an issue. The file contains old, and will be created after an update. As a user, I'd quickly recognize "oh, it's a backup".

[probonopd]

This is what https://github.com/antony-jr/AppImageUpdaterBridge does and I think it's not the worst idea: