Emit exclusion patterns before inclusion patterns - #566

Problem

create_exclude_list_for_backup() writes the user's patterns in the order they appear in config. rsync applies the first pattern that matches, so when a user's list mixes inclusion (+) and exclusion patterns, an inclusion covering a parent directory is written first and every exclusion beneath it becomes unreachable.

The effect is silent: the GUI still displays the excludes as active, but they are not applied to the snapshot.

This is most severe when a network or FUSE filesystem is mounted inside a user's home directory. rsync walks the entire remote filesystem over the network, then exits non-zero on the entries it cannot read. Timeshift discards the snapshot, so no snapshot is created at all.

Reproduction

Config with a parent inclusion plus two exclusions:

"exclude": [
  "+ /home/frank/**",
  "/home/frank/models/***",
  "/home/frank/Desktop/C on Player (NoMachine)/***"
]

Generated exclude.list in 25.12.4 — the + lands on line 1:

+ /home/frank/**
/home/frank/models/***
/home/frank/Desktop/C on Player (NoMachine)/***
...

$ rsync -a --dry-run -v --exclude-from=exclude.list / /dest | grep -c "C on Player"
99772

models/ and the NoMachine mount (an sshfs mount of a Windows C: drive) are both traversed in full, and the snapshot fails with rsync error: errors with program diagnostics (code 13).

Fix

Emit exclusion patterns first and inclusion patterns second. User entries still precede the built-in defaults, so users continue to override them; only the relative order of the user's own entries changes.

Generated exclude.list after the change:

/home/frank/models/***
...
/home/frank/Desktop/C on Player (NoMachine)/***
+ /home/frank/**

Verification

Built and tested on Ubuntu 26.04 (kernel 7.0) against timeshift 25.12.4 / upstream 26.09.0, with the NoMachine sshfs mount actively present.

Before, using the generated exclude.list verbatim:

$ rsync -a --dry-run -v --exclude-from=exclude.list / /dest | grep -c "C on Player"
99772

After:

$ timeshift --create --snapshot-device /dev/sda1
RSYNC Snapshot saved successfully (621s)

• mount skipped: Desktop/ in the snapshot contains only the local file, 0 references to C on Player in the rsync log
• models/ excluded as intended
• 0 rsync errors, previously exit code 13
• 10m21s for a ~66G first snapshot

Scope

Changes only the emission order in create_exclude_list_for_backup(). No changes to pattern parsing, matching, defaults, or the restore path. A user whose list contains only inclusions, or only exclusions, gets a byte-identical exclude.list.

Note for maintainers

create_exclude_list_for_restore() already skips + patterns outright (line 931) and does not have this ordering issue, so it is left unchanged.