The previous approach of rewriting all snapshots first, then flushing
the repository data and finally removing old snapshots has the downside
that an interrupted command execution leaves behind broken snapshots as
not all new data is already flushed.
This adds support for caching already rewritten trees, handling of load
errors and disabling the check that the serialization doesn't lead to
data loss.
The more generic RewriteNode callback replaces the SelectByName and
PrintExclude functions. The main part of this change is a preparation to
allow using the TreeRewriter for the `repair snapshots` command.
The files in a tree must be sorted in lexical order. However, this
cannot be guaranteed when appending a filename suffix. For two files
file, file.rep
where "file" is broken, this would result in
file.repaired, file.rep
which is no longer sorted.
In addition, adding a filename suffix is also prone to filename
collisions which would require a rather complex search for a
collision-free name in order to work reliably.
Simplify CLI options:
* Rename "DeleteSnapshots" to "Forget"
* Replace "AddTag" and "Append" with hardcoded values
Change output and snapshot modifications to be more in line with the
"rewrite" command.
The builtin mechanism to capture a stacktrace in Go is to send a SIGQUIT
to the running process. However, this mechanism is not avaiable on
Windows. Thus, tweak the SIGINT handler to dump a stacktrace if the
environment variable `RESTIC_DEBUG_STACKTRACE_SIGINT` is set.
When saving files to the local backend, in some cases the used fsync
calls are slow enough to cause the tests to time out. Thus, increase the
test timeouts as a stopgap measure until we can use the mem backend for
these tests.
The SemaphoreBackend now uniformly enforces the limit of concurrent
backend operations. In addition, it unifies the parameter validation.
The List() methods no longer uses a semaphore. Restic already never runs
multiple list operations in parallel.
By managing the semaphore in a wrapper backend, the sections that hold a
semaphore token grow slightly. However, the main bottleneck is IO, so
this shouldn't make much of a difference.
The key insight that enables the SemaphoreBackend is that all of the
complex semaphore handling in `openReader()` still happens within the
original call to `Load()`. Thus, getting and releasing the semaphore
tokens can be refactored to happen directly in `Load()`. This eliminates
the need for wrapping the reader in `openReader()` to release the token.
This turns snapshotFilterOptions from cmd into a restic.SnapshotFilter
type and makes restic.FindFilteredSnapshot and FindFilteredSnapshots
methods on that type. This fixes #4211 by ensuring that hosts and paths
are named struct fields instead of unnamed function arguments in long
lists of such.
Timestamp limits are also included in the new type. To avoid too much
pointer handling, the convention is that time zero means no limit.
That's January 1st, year 1, 00:00 UTC, which is so unlikely a date that
we can sacrifice it for simpler code.
The output is now
```
-v, --verbose be verbose (specify multiple times or a level using --verbose=n, max level/times is 2)
```
instead of
```
-v, --verbose n be verbose (specify multiple times or a level using --verbose=n, max level/times is 2)
```
