Add NEWS for 5.3.3alpha.
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XZ Utils Release Notes
======================
+5.3.3alpha (2022-08-22)
+
+ * All fixes from 5.2.6.
+
+ * liblzma:
+
+ - Fixed 32-bit build.
+
+ - Added threaded .xz decompressor lzma_stream_decoder_mt().
+ It can use multiple threads with .xz files that have multiple
+ Blocks with size information in Block Headers. The threaded
+ encoder in xz has always created such files.
+
+ Single-threaded encoder cannot store the size information in
+ Block Headers even if one used LZMA_FULL_FLUSH to create
+ multiple Blocks, so this threaded decoder cannot use multiple
+ threads with such files.
+
+ If there are multiple Streams (concatenated .xz files), one
+ Stream will be decompressed completely before starting the
+ next Stream.
+
+ - A new decoder flag LZMA_FAIL_FAST was added. It makes the
+ threaded decompressor report errors soon instead of first
+ flushing all pending data before the error location.
+
+ * xz:
+
+ - Using -T0 (--threads=0) will now use multi-threaded encoder
+ even on a single-core system. This is to ensure that output
+ from the same xz binary is identical on both single-core and
+ multi-core systems.
+
+ - A default soft memory usage limit is now used for compression
+ when -T0 is used and no explicit limit has been specified.
+ This soft limit is used to restrict the number of threads
+ but if the limit is exceeded with even one thread then xz
+ will continue with one thread using the multi-threaded
+ encoder and this limit is ignored. If the number of threads
+ is specified manually then no default limit will be used;
+ this affects only -T0.
+
+ This change helps on systems that have very many cores and
+ using all of them for xz makes no sense. Previously xz -T0
+ could run out of memory on such systems because it attempted
+ to reserve memory for too many threads.
+
+ This also helps with 32-bit builds which don't have a large
+ amount of address space that would be required for many
+ threads. The default limit is 1400 MiB on all 32-bit
+ platforms with -T0.
+
+ Now xz -T0 should just work. It might use too few threads
+ in some cases but at least it shouldn't easily run out of
+ memory. It's possible that this will be tweaked before 5.4.0.
+
+ - Changes to --memlimit-compress and --no-adjust:
+
+ In single-threaded mode, --memlimit-compress can make xz
+ scale down the LZMA2 dictionary size to meet the memory usage
+ limit. This obviously affects the compressed output. However,
+ if xz was in threaded mode, --memlimit-compress could make xz
+ reduce the number of threads but it wouldn't make xz switch
+ from multi-threaded mode to single-threaded mode or scale
+ down the LZMA2 dictionary size. This seemed illogical.
+
+ Now --memlimit-compress can make xz switch to single-threaded
+ mode if one thread in multi-threaded mode uses too much
+ memory. If memory usage is still too high, then the LZMA2
+ dictionary size can be scaled down too.
+
+ The option --no-adjust was also changed so that it no longer
+ prevents xz from scaling down the number of threads as that
+ doesn't affect compressed output (only performance). After
+ this commit --no-adjust only prevents adjustments that affect
+ compressed output, that is, with --no-adjust xz won't switch
+ from multithreaded mode to single-threaded mode and won't
+ scale down the LZMA2 dictionary size.
+
+ - Added a new option --memlimit-decompress-mt=LIMIT. This is
+ used to limit the number of decompressor threads (possibly
+ falling back to single-threaded mode) but it will never make
+ xz refuse to decompress a file. This has a system-specific
+ default value because without any limit xz could end up
+ allocating memory for the whole compressed input file, the
+ whole uncompressed output file, multiple thread-specific
+ decompressor instances and so on. Basically xz could
+ attempt to use an insane amount of memory even with fairly
+ common files.
+
+ The new option works together with the existing option
+ --memlimit-decompress=LIMIT. The old option sets a hard limit
+ that must not be exceeded (xz will refuse to decompress)
+ while the new option only restricts the number of threads.
+ If the limit set with --memlimit-mt-decompress is greater
+ than the limit set with --memlimit-compress, then the latter
+ value is used also for --memlimit-mt-decompress.
+
+ * Tests:
+
+ - Added a few more tests.
+
+ - Added tests/code_coverage.sh to create a code coverage report
+ of the tests.
+
+ * Build systems:
+
+ - Automake's parallel test harness is now used to make tests
+ finish faster.
+
+ - Added the CMake files to the distribution tarball. These were
+ supposed to be in 5.2.5 already.
+
+ - Added liblzma tests to the CMake build.
+
+ - Windows: Fix building of liblzma.dll with the included
+ Visual Studio project files.
+
+
5.3.2alpha (2021-10-28)
This release was made on short notice so that recent erofs-utils can
