Problem:  'diffopt' "linematch" cannot be used with {n} less than 10
          digits (after v9.1.1022)
Solution: Fix off-by-one error when checking for digit (zeertzjq)

closes: vim/vim#16577

https://github.com/vim/vim/commit/ccd7f454fcac2f99085d4f50e79c111c02741166

Problem:  no sanitize check when running linematch
Solution: add sanitize check before applying the linematch algorithm,
          similar to diff_find_change() (Jonathon)

closes: vim/vim#16446

https://github.com/vim/vim/commit/ca307efe486670b76563a4a287bc94dace57fb74

Co-authored-by: Jonathon <jonathonwhite@protonmail.com>

Problem:  linematch option value not completed
          (after v9.1.1009)
Solution: Update diffoption completion values

related: vim/vim#9661
closes: vim/vim#16437

https://github.com/vim/vim/commit/9162e636b31dcac57876cbdec15a683cedd9760e

Co-authored-by: Christian Brabandt <cb@256bit.org>

Problem:  diff feature can be improved
Solution: include the linematch diff alignment algorithm
          (Jonathon)

closes: vim/vim#9661

https://github.com/vim/vim/commit/7c7a4e6d1ad50d5b25b42aa2d5a33a8d04a4cc8a

Co-authored-by: Jonathon <jonathonwhite@protonmail.com>

Problem:  Strange error when heredoc marker starts with "trim".
Solution: Check for whitespace after "trim" or "eval" (zeertzjq)

For :python3 etc., a heredoc marker that starts with a lower-case letter
is valid, and when it starts with "trim" it works in a script but not in
a function, and this PR makes it works in a function.
For :let, a heredoc marker that starts with a lower-case letter is not
valid, but when it starts with "trim" or "eval" the error can be a bit
confusing in a function, and this PR make it less confusing.

closes: vim/vim#16574

https://github.com/vim/vim/commit/449c2e5454735fe1cfc8c21b2c6880d6bdf4cd6e

Problem:  tests: test_compiler fails on Windows without Maven.
Solution: Add Xspotbugs directory to $PATH when mvn is not available
          (zeertzjq).

closes: vim/vim#16576

https://github.com/vim/vim/commit/23da16d3d023a20565dc29128208e6cb095231d9

Problem:  SpotBugs compiler can be further improved
Solution: Introduce event-driven primitives for SpotBugs
          (Aliaksei Budavei)

closes: vim/vim#16258

https://github.com/vim/vim/commit/2e252474c4df5018b9819d86ebb70bf3b1b1a1af

Co-authored-by: Aliaksei Budavei <0x000c70@gmail.com>

Problem:  SpotBugs compiler can be improved
Solution: runtime(compiler): Improve defaults and error handling for
          SpotBugs; update test_compiler.vim (Aliaksei Budavei)

runtime(compiler): Improve defaults and error handling for SpotBugs

* Keep "spotbugs#DefaultPreCompilerTestAction()" defined but
  do not assign its Funcref to the "PreCompilerTestAction"
  key of "g:spotbugs_properties": there are no default and
  there can only be introduced arbitrary "*sourceDirPath"
  entries; therefore, this assignment is confusing at best,
  given that the function's implementation delegates to
  whatever "PreCompilerAction" is.

* Allow for the possibility of relative source pathnames
  passed as arguments to Vim for the Javac default actions,
  and the necessity to have them properly reconciled when
  the current working directory is changed.

* Do not expect users to remember or know that new source
  files ‘must be’ ":argadd"'d to be then known to the Javac
  default actions; so collect the names of Java-file buffers
  and Java-file Vim arguments; and let users providing the
  "@sources" file-lists in the "g:javac_makeprg_params"
  variable update these file-lists themselves.

* Strive to not leave behind a fire-once Syntax ":autocmd"
  for a Java buffer whenever an arbitrary pre-compile action
  errors out.

* Only attempt to run a post-compiler action in the absence
  of failures for a pre-compiler action.  Note that warnings
  and failures are treated alike (?!) by the Javac compiler,
  so when previews are tried out with "--enable-preview",
  remember about passing "-Xlint:-preview" too to also let
  SpotBugs have a go.

* Properly group conditional operators when testing for key
  entries in a user-defined variable.

* Also test whether "javaExternal" is defined when choosing
  an implementation for source-file parsing.

* Two commands are provided to toggle actions for buffer-local
  autocommands:
  - SpotBugsRemoveBufferAutocmd;
  - SpotBugsDefineBufferAutocmd.

For example, try this from "~/.vim/after/ftplugin/java.vim":
------------------------------------------------------------
if exists(':SpotBugsDefineBufferAutocmd') == 2
	SpotBugsDefineBufferAutocmd BufWritePost SigUSR1
endif
------------------------------------------------------------

And ":doautocmd java_spotbugs User" can be manually used at will.

closes: vim/vim#16140

https://github.com/vim/vim/commit/368ef5a48c7a41af7fe2c32a5d5659e23aff63d0

Co-authored-by: Aliaksei Budavei <0x000c70@gmail.com>

Problem:  Arguments of a function are missing after failing to redefine
          it (after 8.2.2505), and heap-use-after-free with script-local
          function (after 9.1.1063).
Solution: Don't clear arguments or free uf_name_exp when failing to
          redefine an existing function (zeertzjq)

closes: vim/vim#16567

https://github.com/vim/vim/commit/04d2a3fdc051d6a419dc0ea4de7a9640cefccd31

Problem:  heap-use-after-free and stack-use-after-scope with :14verbose
          when using :return and :try (after 9.1.1063).
Solution: Move back the vim_free(tofree) and the scope of numbuf[].
          (zeertzjq)

closes: vim/vim#16563

https://github.com/vim/vim/commit/2101230f4013860dbafcb0cab3f4e6bc92fb6f35