* lib/model: Don't panic on failed chmod-back on directory (fixes#5836)
This makes the "in writable dir"-wrapper log chmod-back errors instead
of panicking. To do that we need a logger so the function moved into the
model package which is also the only place it's used. The tests came
along.
(The test also exercised osutil.RenameOrCopy like some sort of
piggybacking. I removed that.)
I'm working through linter complaints, these are some fixes. Broad
categories:
1) Ignore errors where we can ignore errors: add "_ = ..." construct.
you can argue that this is annoying noise, but apart from silencing the
linter it *does* serve the purpose of highlighting that an error is
being ignored. I think this is OK, because the linter highlighted some
error cases I wasn't aware of (starting CPU profiles, for example).
2) Untyped constants where we though we had set the type.
3) A real bug where we ineffectually assigned to a shadowed err.
4) Some dead code removed.
There'll be more of these, because not all packages are fixed, but the
diff was already large enough.
This adds a folder option "CopyOwnershipFromParent" which, when set,
makes Syncthing attempt to retain the owner/group information when
syncing files. Specifically, at the finisher stage we look at the parent
dir to get owner/group and then attempt a Lchown call on the temp file.
For this to succeed Syncthing must be running with the appropriate
permissions. On Linux this is CAP_FOWNER, which can be granted by the
service manager on startup or set on the binary in the filesystem. Other
operating systems do other things, but often it's not required to run as
full "root". On Windows this patch does nothing - ownership works
differently there and is generally less of a deal, as permissions are
inherited as ACLs anyway.
There are unit tests on the Lchown functionality, which requires the
above permissions to run. There is also a unit test on the folder which
uses the fake filesystem and hence does not need special permissions.
In a recent change (#5201) this return disappeared. The effect is that
we first shortcut the file and then also treat it normally. This results
in to database updates after each other, which are bound to end up in
the same batch. This means we remove one sequence entry and add two.
Not marking the issues as fixed, because I need to do more testing and
there are other discrepancies...
