Before this change, bisync could only detect changes based on modtime, and
would refuse to run if either path lacked modtime support. This made bisync
unavailable for many of rclone's backends. Additionally, bisync did not account
for the Fs's precision when comparing modtimes, meaning that they could only be
reliably compared within the same side -- not against the opposite side. Size
and checksum (even when available) were ignored completely for deltas.
After this change, bisync now fully supports comparing based on any combination
of size, modtime, and checksum, lifting the prior restriction on backends
without modtime support. The comparison logic considers the backend's
precision, hash types, and other features as appropriate.
The comparison features optionally use a new --compare flag (which takes any
combination of size,modtime,checksum) and even supports some combinations not
otherwise supported in `sync` (like comparing all three at the same time.) By
default (without the --compare flag), bisync inherits the same comparison
options as `sync` (that is: size and modtime by default, unless modified with
flags such as --checksum or --size-only.) If the --compare flag is set, it will
override these defaults.
If --compare includes checksum and both remotes support checksums but have no
hash types in common with each other, checksums will be considered only for
comparisons within the same side (to determine what has changed since the prior
sync), but not for comparisons against the opposite side. If one side supports
checksums and the other does not, checksums will only be considered on the side
that supports them. When comparing with checksum and/or size without modtime,
bisync cannot determine whether a file is newer or older -- only whether it is
changed or unchanged. (If it is changed on both sides, bisync still does the
standard equality-check to avoid declaring a sync conflict unless it absolutely
has to.)
Also included are some new flags to customize the checksum comparison behavior
on backends where hashes are slow or unavailable. --no-slow-hash and
--slow-hash-sync-only allow selectively ignoring checksums on backends such as
local where they are slow. --download-hash allows computing them by downloading
when (and only when) they're otherwise not available. Of course, this option
probably won't be practical with large files, but may be a good option for
syncing small-but-important files with maximum accuracy (for example, a source
code repo on a crypt remote.) An additional advantage over methods like
cryptcheck is that the original file is not required for comparison (for
example, --download-hash can be used to bisync two different crypt remotes with
different passwords.)
Additionally, all of the above are now considered during the final --check-sync
for much-improved accuracy (before this change, it only compared filenames!)
Many other details are explained in the included docs.
Before this change, integration tests often could not be run on backends with
differing features from the local system that goldenized them. In particular,
differences in modtime precision, checksum support, and encoding would cause
false positives. After this change, the tests more accurately account for the
features of the backend being tested, which allows us to see true positives
more clearly, and more meaningfully assess whether a backend is supported.
Before this change, --resync was handled in three steps, and needed to do a lot
of unnecessary work to implement its own --ignore-existing logic, which also
caused problems with unicode normalization, in addition to being pretty slow.
After this change, it is refactored to produce the same result much more
efficiently, by reducing the three steps to two and letting ci.IgnoreExisting
do the work instead of reinventing the wheel.
The behavior and sync order remain unchanged for now -- just faster (but see
the ongoing lively discussions about potential future changes in #5681!)
Before this change, bisync needed to build a full listing for Path1, then a
full listing for Path2, then compare them -- and each of those tasks needed to
finish before the next one could start. In addition to being slow and
inefficient, it also caused real problems if a file changed between the time
bisync checked it on Path1 and the time it checked the corresponding file on
Path2.
This change solves these problems by listing both paths concurrently, using
the same March infrastructure that check and sync use to traverse two
directories in lock-step, optimized by Go's robust concurrency support.
Listings should now be much faster, and any given path is now checked
nearly-instantaneously on both sides, minimizing room for error.
Further discussion:
https://forum.rclone.org/t/bisync-bugs-and-feature-requests/37636#:~:text=4.%20Listings%20should%20alternate%20between%20paths%20to%20minimize%20errors
This introduces a few basic color codings to make the terminal output more
readable (and more fun). Rclone's standard --color flag is supported.
(AUTO|NEVER|ALWAYS)
Only a few lines have colors right now -- more will probably be added in
future versions.
Before this change, bisync handled copies and deletes in separate operations.
After this change, they are combined in one sync operation, which is faster
and also allows bisync to support --track-renames and --backup-dir.
Bisync uses a --files-from filter containing only the paths bisync has
determined need to be synced. Just like in sync (but in both directions),
if a path is present on the dst but not the src, it's interpreted as a delete
rather than a copy.
