Incomplete search path(s) for xdelta3 executable

[Svet Bajlekov]

When determining whether to use deltas or do a full snap download, snapd verifies that an xdelta3 executable is available. However it appears to only look for xdelta3 in (a) the system path, and (b) the core snap.

So in a situation where xdelta3 is not installed in the system path, and the snapd snap is used instead of the core snap, snapd's xdelta3 executable is not found. As a result, snapd does not use deltas but instead does full downloads.

The relevant code for 2.43.3 is at
https://github.com/snapcore/snapd/blob/2.43.3/store/store.go#L1678-L1686
under the getXdelta3Cmd function. Presumably a potential fix is to add filepath.Join(dirs.SnapMountDir, "/snapd/current/usr/bin/xdelta3") to the list of paths being searched.

[Zygmunt Krynicki (zyga)]

This is fixed by https://github.com/snapcore/snapd/pull/8175 and is now in master.

[Zygmunt Krynicki (zyga)]

This was fixed in snapd 2.44 which was since released. Marking it as such.