am--refresh target assumed to be provided by top-level Makefile is not documented

[Samuel Bronson]

Hi. I've noticed that when trying to build gdb from git with
--enable-maintainer-mode, I get this error:

make[2]: Entering directory `/home/naesten/hacking/archer/build/gdb'
CONFIG_FILES="gnulib/Makefile" \
          CONFIG_COMMANDS="depfiles" \
          CONFIG_HEADERS= \
          CONFIG_LINKS= \
          /bin/sh config.status
config.status: creating gnulib/Makefile
config.status: executing depfiles commands
make[3]: Entering directory `/home/naesten/hacking/archer/build/gdb'
make[4]: Entering directory `/home/naesten/hacking/archer/build/gdb/gnulib'
cd .. && make  am--refresh
make[5]: Entering directory `/home/naesten/hacking/archer/build/gdb'
make[5]: *** No rule to make target `am--refresh'.  Stop.
make[5]: Leaving directory `/home/naesten/hacking/archer/build/gdb'
make[4]: *** [../../../gdb/configure] Error 2
make[4]: Leaving directory `/home/naesten/hacking/archer/build/gdb/gnulib'
make[3]: *** [subdir_do] Error 1
make[3]: Leaving directory `/home/naesten/hacking/archer/build/gdb'
make[2]: *** [all-lib] Error 2
make[2]: Leaving directory `/home/naesten/hacking/archer/build/gdb'
make[1]: *** [all-gdb] Error 2
make[1]: Leaving directory `/home/naesten/hacking/archer/build'
make: *** [all] Error 2
make: Leaving directory `/home/naesten/hacking/archer/build'

It seems that automake assumes that the top-level Makefile for a
project (that is, the one that sits next to the configure script --
generated from gdb/Makefile.in in this case) will provide an
"am--refresh" target, which no doubt it would if the top-level
Makefile.in was generated by automake. However, I could find nothing
in the automake documentation about either am--refresh or needing to
have the top-level Makefile.in generated by automake, and Tom Tromey
said he wasn't aware of any such requirement either.

The Makefile.in in question was generated with automake 1.9.6, and
regenerating it doesn't make any difference as long as I touch the
Makefile.am afterwards to keep Makefile.in considered out-of-date.

What exactly does automake expect from this am--refresh target, so I
can write one to keep it happy without having to use automake to
generate gdb/Makefile.in ?

Also ... why doesn't the output of "automake --version" list the
current automake maintainer, if Tom Tromey doesn't maintain it
anymore?