Fix rsync issues with quotes in remote path

[FMeinicke]

I recently noticed that my scheduled backups were failing because of a rsync error. Here's the log output:

[I] ...
[I] Take snapshot
[I] rsync --recursive --times --devices --specials --hard-links --human-readable --links --perms --executability --group --owner --rsh=ssh -o ServerAliveInterval=240 -o LogLevel=Error -o IdentityFile=/home/florian/.ssh/id_rsa -p 22 --delete --delete-excluded -v -i --out-format=BACKINTIME: %i %n%L --link-dest=../../20220516-210001-824/backup --chmod=Du+wx --exclude=... --include=... / Florian@my_server:"backups/backintime/manjaro/florian/1/new_snapshot/backup"
[I] Take snapshot (rsync: sending incremental file list)
[I] Take snapshot (rsync: rsync: mkdir "/volume1/homes/Florian/"backups/backintime/manjaro/florian/1/new_snapshot/backup"" failed: No such file or directory (2))
[E] Error: rsync: mkdir "/volume1/homes/Florian/"backups/backintime/manjaro/florian/1/new_snapshot/backup"" failed: No such file or directory (2)
[I] Take snapshot (rsync: rsync error: error in file IO (code 11) at main.c(615) [Receiver=3.0.9])
[I] Take snapshot (rsync: rsync: connection unexpectedly closed (215 bytes received so far) [sender])
[I] Take snapshot (rsync: rsync error: error in rsync protocol data stream (code 12) at io.c(228) [sender=v3.2.4])

Just for reference: The SSH server I'm backing up to is a Synology NAS.

The problem is that rsync seems unable to handle the quotes in Florian@my_server:"backups/backintime/manjaro/florian/1/new_snapshot/backup". Removing the quotes resulted in a successful backup again.

I don't know whether my local rsync or the remote rsync changed behavior in a newer version. For reference here are the rsync versions I'm using:
local

$ rsync --version
rsync  version v3.2.4  protocol version 31
Copyright (C) 1996-2022 by Andrew Tridgell, Wayne Davison, and others.
Web site: https://rsync.samba.org/
Capabilities:
    64-bit files, 64-bit inums, 64-bit timestamps, 64-bit long ints,
    socketpairs, symlinks, symtimes, hardlinks, hardlink-specials,
    hardlink-symlinks, IPv6, atimes, batchfiles, inplace, append, ACLs,
    xattrs, optional protect-args, iconv, prealloc, stop-at, no crtimes
Optimizations:
    SIMD-roll, no asm-roll, openssl-crypto, no asm-MD5
Checksum list:
    xxh128 xxh3 xxh64 (xxhash) md5 md4 none
Compress list:
    zstd lz4 zlibx zlib none

remote

$ rsync --version
rsync  version 3.0.9  protocol version 30
Copyright (C) 1996-2011 by Andrew Tridgell, Wayne Davison, and others.
Web site: http://rsync.samba.org/
Capabilities:
    64-bit files, 64-bit inums, 64-bit timestamps, 64-bit long ints,
    no socketpairs, hardlinks, symlinks, IPv6, batchfiles, inplace,
    append, no ACLs, xattrs, iconv, no symtimes

I assume the purpose of the quotes is to support paths with spaces. So, to achieve the same behavior as before there is the --protect-args option in rsync which allows using paths with spaces without having to surround them with additional quotes.

This PR adds the --protect-args flag to the rsync command and removes all explicit quotes around remote paths.
I don't know if changing the default value of the quote parameter in rsyncRemotePath is the preferred solution but it was the easiest for me to do. :D

I tested this with my setup using a remote backup path with and without spaces and it worked just as before.

Just FYI: I also found the suggestion that quoting the whole user@host:path (i.e. "Florian@my_server:backups/backintime/manjaro/florian/1/new_snapshot/backup" in my case) should work but this didn't seem to be the case here.

[buhtz]

I assume this is related to #1247 .

[FMeinicke]

Yep. this is related.

It seems like my solution would potentially break with rsync<3.2.4, though. I saw in #1247 that you're currently working on a backward compatible fix. Since I'm okay with using the workarounds (RSYNC_OLD_ARGS or --old-args) posted there I'm going to close this.