from ChangeLog:
(most of this by rillig@)
o lots of style and white-space cleanup
o lots more unit tests for variable modifiers
o simplified description of some functions
o str.c: refactor Str_Match
o var.c: debugging output for :@
constify VarModify parameter
fix :hash modifier on 16-bit platforms
remove unnecessary forward declarations
refactor ApplyModifier_SysV to have less indentation
simplify code for :E and :R
clean up code for :H and :T
refactor ApplyModifiers
* var.c: we need stdint.h on some platforms to get uint32_t
* unit-test/Makefile: we need to supress the specific error
for RE substitution error in modmisc, since it varies accross
different OS.
Changes since 20181221 are mostly portability related
hence the large gap in versions imported.
There are however some bug fixes, and a rework of filemon handling.
In NetBSD make/filemon/filemon_ktrace.c allows use of fktrace
and elimination of filemon(4) which has not had the TLC it needs.
FreeBSD filemon(4) is in much better shape, so bmake/filemon/filemon_dev.c
allows use of that, with a bit less overhead than the ktrace model.
Summary of changes from ChangeLog
o str.c: empty string does not match % pattern
plus unit-test changes
o var.c: import handling of old sysV style modifier using '%'
o str.c: refactor brk_string
o meta.c: meta_oodate, CHECK_VALID_META is too aggressive for CMD
a blank command is perfectly valid.
o meta.c: meta_oodate, check for corrupted meta file
earlier and more often.
* meta.c: meta_compat_parent check for USE_FILEMON
patch from Soeren Tempel
o meta.c: fix compat mode, need to call meta_job_output()
o job.c: extra fds for meta mode not needed if using filemon_dev
o meta.c: avoid passing NULL to filemon_*() when meta_needed()
returns FALSE.
o filemon/filemon_{dev,ktrace}.c: allow selection of
filemon implementation. filemon_dev.c uses the kernel module
while filemon_ktrace.c leverages the fktrace api available in
NetBSD. filemon_ktrace.c can hopefully form the basis for
adding support for other tracing mechanisms such as strace on
Linux.
o meta.c: when target is out-of-date per normal make rules
record value of .OODATE in meta file.
o parse.c: don't pass NULL to realpath(3)
some versions cannot handle it.
o parse.c: ParseDoDependency: free paths rather than assert
plus more unit-tests
Interesting changes (from ChangeLog):
o meta.c: ignore paths that match .MAKE.META.IGNORE_PATTERNS
this is useful for gcov builds.
o propagate errors from filemon(4).
o meta.c: apply realpath() before matching against metaIgnorePaths
o allow makefile to set .MAKE.JOBS
