I pushed the changes here with some small fixups.

These changes are good as far as they go but I think there are still some remaining issues to be addressed.  I will raise this on the mailing list before closing this issue.

Paul, i attached fix2 and test2. fix2 is split into 2 parts to ease review. Should be applied in order part1 before part2. Thanks for review.

Rob, that's right. The patch fixes both. In fact, this bug report is a duplicate of https://savannah.gnu.org/bugs/?36486.

Markus Oberhumer reported a bug.

Appending to a pattern specific variable produces an incorrect value in the
presence of a command line definition or an env override of the variable.

$ ls
makefile
$ cat makefile
al%: hello+=pattern
all:; $(info hello=$(hello))
$ # this is the lastest make from master
$ ~/src/make/m64/make hello=cmd
hello=cmd cmd
make: 'all' is up to date.
$

The following takes place.
1. At parse time record_target_var sets the value of a pattern specific
variable to the value defined on command line or to the value of the env
override.
2. Later, at build time, recursively_expand_for_file appends this value of the
variable (set in record_target_var) to the command line value again, regardless
of the origin of the variable.


This patch modifies recursively_expand_for_file to avoid appending, unless the
origin of the variable beats or equals the origin of one of the parent
definitions of this variable.

Even though this bug and fix are not related to sv 64803, the test attached
here tests (among other things) appending in the presence of an env override.
That test requires the fix from sv 64803 to pass.

The original bug report is here
https://lists.gnu.org/archive/html/bug-make/2023-09/msg00015.html.