This one regulates the build wrapper: if the value is non-empty
then nice(1) and ionice(1) will be attempted so that the build
behaves better in regard to other tasks running on the system.

A few doc/variables.txt updates along the way.

Back then I didn't come up with anything smarter than
"mkimage-profiles 2.0" (with my tongue in a cheek),
but as m-p has grown up to 0.4 it's time to fix this.

When done properly, all of the string should be brandable
(with some sane default value inheriting from image name),
but let's do it at least bit by bit.

Thanks torabora@ for yet again seemingly obvious feature request
which strangely managed to evade implementation before.

On an afterthought, mass builds would suggest too much coffee
instead of a progress indicator -- so implemented the latter.

NB: the actual downstream-make-calling rule would expand the "naive"
$(shell date) too early: the rule is evaluated before starting its
execution, and as it's the time consuming one the shell evaluation
was in need, not make's.  The result is less generally available
(needs to be double quoted and won't work inside e.g. awk programs)
but way more precise.

The seemingly obvious feature was proposed by torabora@.
APTCONF complicates things a bit of course...
(and was slightly kludgy btw; fixed)

Also added to the live-builder ISO which is now self-hosted
(sans full repo): one can build an image capable of rebuilding
itself (which is not that useful) and of building other goodies
on some temporarily unused RAM-filled hardware (which is the goal).

If you make distro/live-builder.iso, the result is an image
containing almost everything (short of actual full enough
repository) to rebuild itself.  It will attempt to configure
eth0 with DHCP and reach http://ftp.altlinux.org for packages.

RAM requirements start with 2Gb, self-build is accomplished
on a 4Gb host with "make CLEAN=1 distro/live-builder.iso".

Packages required for "make distro/syslinux.iso" get included.

(some due fixups all over the place too)

With not-that-recent mkimage-profiles development,
it's no longer apparent that at least a gigabyte
of free space is required to build something useful
(at least for the tests, like syslinux.iso).

In short, the guesser cutoff margin is now 256M.

Unfortunately apt configuration is not straightforward at all
regarding being overridden: one can't just provide sources.list
but needs a corresponding apt.conf along with it, and that apt.conf
must disable the SysV-style snippet directories to avoid interesting
side effects of all the things getting overlaid.

So it's not surprising that torabora has asked for an example...
(thanks go to boyarsh@ since I asked him for an example long ago)

Implemented opportunistic alarm support as proposed by torabora;
the actual result depends on readline and/or terminal settings
(read up on "visual bell" vs "audible bell" in case it's wrong).

TODO: this ought to be shifted downstream when proper logging
framework is there.

This was asked for by Leo-sp50 and torabora, and seems quite reasonable:
let's provide means to keep at least some distribution configurations
a bit apart, so that these can be considered more standalone in terms
of hard warranted functionality but at the same time enjoying the common
infrastructure.

Considering lib/distro.mk: it's now experimentally pulled apart so that
parallel development of different distro families can go on without
major merge hassles.  *Please* don't abuse with massive copy-paste.

And before you ask: this might get extended to allow for "private"
out-of-tree configurations being included since apparently there
are goals with no meaning outside of some very particular context...
but otherwise I'd like to encourage getting reusable bits in-tree.

Employed double colon targets to eliminate
  warning: ignoring old commands for target `debug'

The same change as in m-p-d f1c5dd0 (discussed in #22486).
Seems it wasn't the culprit regarding the "BIOS won't boot
off this DVD" but is also recommended in README.gfxboot.

Borrowed from wmsmall iso by kostyalamer@.

src/dst tags might have been empty confusing tags2lists;
the current implementation is more robust (along with
slightly better debug within bin/tags2lists itself).

pushd/popd spam tamed too (replaced by nice log messages).

...and create a symlink to a just-built image from builddir too.

If the build is (re-)run withing generated profile directory,
the makefiles no longer have ARCH passed by upstream -- the
upstream might be unreachable at that point indeed.

This is unfortunate but we should cope with that.

NB: might be revisited when architecture-specific packagelists emerge
since currently there's no difference in package lists so we can just
re-run the build for a different architecture but this might change...

Typical (to-be-refactored when having settled down)
"cd/git .../cd -" sequences are tweaked to safeguard
against changing back without having actually changed to,
just in case.

features.in/Makefile left with pushd/popd due to its
three-level diving course (which somewhat asks to be
refactores in functions either but is intrinsically
somewhat complex OTOH).

This is quite a large-scale change since mkimage-profiles got used to
baking distributions over the last year, and virtual environments are
quite different, so e.g. image.in/Makefile had to be split in two with
the main part of it moved into features.in/iso/lib/.

Short overview:

- features.in/Makefile: lib/ support
  (supporting VE images requires dynamic modifications
  to image.in/Makefile before starting the build;
  the most natural way to achieve that seems to use
  features mechanism along with makefile include dir)

- packaging format related part moved into features.in/pack
  (should be better prepared for diversity either)
- features.in/iso renamed to features.in/build-distro
- features.in/ve  renamed to features.in/build-ve
  + NB: these could not be merged as e.g. features.in/build
    due to completely different script hooks

- lib/image.mk renamed to lib/build.mk
- image, config, log postprocessing moved downstream
- added a sort of a topping in the form of lib/sugar.mk
- assorted style fixups (like ifeq usage)

- clean.mk: reliability fix (the problem was observed by Oleg Ivanov
  and me too but finally it did get the attention quantum)

- reviewed, updated and extended docs
  + QUICKSTART: should be[come] a step-by-step guide
    (thanks Leo-sp50 for prodiving feedback)

install2 cleanups:

- functionally indifferent ones: particularly, install2/*/98system's
  "mkdir -p /image" was superfluous as it was done by that time already
  by sub.in/stage2/image-scripts.d/00stage1

- taken apart, prepared for tags: so far it's a mostly moot change
  since the installer cleanup scripts themselves are mostly the same as
  preceding 90cleanup was (with some additions corresponding to recent
  kernel development); it's still unclear what the mechanism for
  configuring the cleanups in effect will be, either directory/package
  regex lists or tagged scripts excluded from execution by yet another tag

fixes:

- image.in/Makefile: fix metadata related test; the actual test was
  assuming that stage1 kernel means installer, which is not the case
  since generic stage2 introduction; oh well

- 85cleanup-lowmem: a "_" too much was the culprit in destroying the
  needed translations along with those deemed superfluous; thanks go to
  Oleg Ivanov and Lenar Shakirov for finding the bug and proposing the
  fix altogether

additions:

- features.in/Makefile: reworked help target; it was rather inaccessible
  due to BUILDDIR normally undefined at the time of direct make
  invocation, and BUILDDIR is normally defined during normal builds
  anyways so let's try it this way.

- README++

daydreams:

- 01-genbasedir: we should drop bzip2 compressed pkglists some day
  but see genbasedir and apt-cdrom first, 90-pkg.sh (alterator-pkg)
  will fail miserably otherwise

Just in case the build.log will be inobvious, and it's easy to diagnose
automatically.  Thanks Andrey Stroganov for this use case.

Thanks for improving the initial implementation go to raorn@ for kind
commit lynch and to Yuri Bushmelev for actually suggesting something
more concise.

BTW the "1024" magic number was taken out of thin air:
the "no free space" errors are most likely to happen while
forming/populating a chroot (apt/rpm errors out) and chroots are
roughly two orders of magnitude heftier than a megabyte.

"echo ... | xargs cp -t" is a bit more complicated
compared to plain "copy ..."

The extra tag to filter on was omitted while
moving the code from features.in/cleanup/generate.mk
into the more generic features.in/Makefile; fixed.

Auto-added tags will definitely see an overhaul
when it's more clear what can be done with them.

The reason not to add server cleanup right into
distro/server-base is the possibility to build
combined installers (read centaurus).
Gotta sort it out some day...

Applying set() and only set() to a GLOBAL_* is safe
but still a potentially confusing example; so let's
just do it right (and warn unsuspecting folks too).

This was done while debugging GLOBAL_CLEANUP_PACKAGES
getting doubled... as it got no hard initial value but
rather was always added to, it appeared that at least
stage2/Makefile would obtain a once-initialized value
from upstream and double it while including distcfg.mk
itself.

It's way less hassle to just proxy the value once.

This is a sort of anti-feature which removes and not builds;
still with mkimage-profiles' approach we can at least build
up the removal procedures as well.

It's what triggered the tagged scripts, BTW.

From now on a feature can contain this tree:

.
+- scripts.d/
+- image-scripts.d/
`- tagged/
   +- scripts.d/
   `- image-scripts.d/

...per subprofile part or in its root -- the latter one
gets merged into toplevel directory responsible for the
final image build.

NB: autoselected tags include only subprofile names
    (or both parts, for complex subprofiles) --
    this is highly prone to change yet!

Mostly needed for tags2lists at the moment;
note that PATH is exported for make recipes
but has no effect on make functions.

$(IMAGES) in prerequisites definitely won't work,
so let's do it straightforward.

The docs would be purged anyways, let's not install them either.

Somewhat more uniform style and a few additional bits.

Introduced support for hooks to be added to every
derivative substage of a "base" stage (think stage2/*).

Specific hooks for e.g. stage2/live would live in
features.in/*/live/*scripts.d/ while generic for stage2/* in
features.in/*/stage2/*scripts.d/

(these *really* should be added atomically with the changes!)

This was tackled before but it took raorn@'s hint regarding
sys-freedos-linux (ms-sys has no bootsectors compatible with
freedos currently) and gns@' quick rush at make-freedos-floppy
script to wrap things up.

Should be further developed to become actually useful though.

wm-select should only be needed when multiple window managers
are available.

Should support ACPI and APM schemes;
only the former tested so far.

It was clear that "common" isn't very apt for packages that
will get *everywhere*, and became apparent when the need for
a "base+live packages" variable arrived with powerbutton feature.

So:
- the former COMMON_PACKAGES are now SYSTEM_PACKAGES;
- COMMON_PACKAGES act as "BASE+LIVE_PACKAGES".

Note that SYSTEM_PACKAGES also got factored out from stage2 based
features into stage2 subprofile itself; cleanups were due as well.

Rather minor fixups for things changed in the meanwhile and not
yet (re)documented properly; and a change for memtest feature
to require syslinux feature (the code's been changed to fit
the updated description, actually, and the change is purely
formal as no syslinux alternative is being used/planned so far).

distcfg.mk is nice for tracing the variable values' build-up,
but it's more useful to have a look at the final result sometimes.
So here it is, logged for each build and callable by hand.

It turned out that ~/out masked the broken execution path
when it's absent (which was handled incompletely).  Sigh.