Also, move some functions from stream to filesystem where they belong.

Also, separate filesystem access functions from pathname object munging.

Optimize probe-file* in the case we do not care for truename.
Have truenamize iterate from pathname up to root rather than the other way,
to minimize the number of calls to truename.
Refactor pathname absolutization.
Shuffle functions around os, pathname, stream.
Shuffle functions around common-lisp, utility.
Remove root-pathname and sane-physical-pathname.

Introduce some backward incompatibility with features unused in quicklisp:
* Don't create a temporary package every time you load a .asd;
 instead, load everything from same package ASDF-USER,
 that :use's asdf/common-lisp asdf/package asdf/interface
 That's the Common Lisp way, what with COMMON-LISP-USER.
 If you want a private package, use DEFPACKAGE or DEFINE-PACKAGE.
* operation-description is renamed action-description.
 No one was using it in quicklisp, and no one was specializing it
 except cl-protobufs, which I'll fix.
* component-properties and component-property are gone.
 If you want a new property, create your own subclass of component.

Also, have a load-asd function with name in keyword arguments,
rather than load-sysdef function that requires the name.

Also, move entry-point into system and remove class bundle-system.
I was tempted to have test-op call it, but then it's a problem
when the base system has a non-test entry-point, so we probably need
a separate test-entry-point slot.

Update the default *asdf-debug-utility* to do more of the right thing.

Update changelog.

Tweak package to avoid triggering a bug in ABCL trunk.

A better asdf.asd.

Refactor the preloaded system mechanism, use it for cl-launch 3.21.2.

Rename bundle-pathname to build-pathname, move it from bundle-system to system.

Rename the gcl<2.7 feature gcl2.6. Die on gcl2.5 and earlier.
Don't even try to compile-file asdf using gcl 2.6, just load the .lisp.

Rename asdf/compatibility to asdf/common-lisp, exporting only CL symbols.
Fix define-package to correctly handle exporting of NIL.

Also, make it work with Genera, with #'(lambda instead of (lambda,
and using lisp:loop (via a macro loop*) when destructuring is required.

Document more 2.27 changes in changelog.

If there is no :pathname and no load-pathname,
do NOT have a system pathname take defaults from *default-pathname-defaults*,
but make it NIL.

unless we're backward compatible.

A system named foo/bar will be looked up in a registered file foo.asd.
This makes it possible to sensibly name several systems in a .asd file
and still have asdf find them all by name.
We now use it to not have the asdf header be part of asdf-driver.

A new generic operation build-op makes it possible to deal with
the fact that the default operation for systems need not be load-op,
yet that the end-user does not want to have to know the exact operation
for each of the system he uses.

ensure-pathname has been improved again, and its clients tweaked.

remove-keys was made more sensible by using EQL rather than STRING-EQUAL.

:version need not take the first form in a file, but can take
a path to a subform. This makes it possible to get the exact subform
in a Lisp source file that has the string.
See SUB-OBJECT for how these paths work.

Cleanup of the semantics of ENSURE-FUNCTION on CONSes: use APPLY, not EVAL.

Move things around and rename functions to improve backward compatibility.
The driver now has its own backward-compatibility file.

* Pathname support has been cleaned up, yet again,
 extending and renaming COERCE-PATHNAME into PARSE-UNIX-NAMESTRING,
 also ENSURE-PATHNAME, many docstrings, and plenty of small enhancements.
* Bundles were refactored to take advantage of the new, more sensible,
 component-depends-on semantics.
* Image support was cleaned up again, and program-op was implemented
 to produce a standalone executable on supported platforms;
 a working hello-world-example is included amongst tests.
* The *compile-file-function* indirection was removed, with the
 ECL and MKCL object file support
 being folded into compile-file* instead.
* systems now can have NIL as component-pathname,
 instead of providing a non-sensible bogus pathname
 when no sensible pathname was determined.
 Most of our pathname functions have sensible default behavior
 when provided NIL instead of a pathname as an argument.

Much cleanup in image support and hooks.
More package hacking.
New feature for :version: `(:read-file-from ,path) - thanks to Stelian Ionescu.
The driver now homesteads the package nickname d.
Rename-package it away if you don't like it.

Tests: SBCL passes test-lisp and test-upgrade
Also:
* big refactoring of test infrastructure
* contrib/debug.lisp and (asdf/driver:asdf-debug) for debugging.
* remove aif and it, use the cleaner if-bind.
* backtrace support, with improvements from trivial-backtrace.
* integration of asdf-condition-control (originally from xcvb-driver)
* simplify the upgrade heuristic: always tries to upgrade once.
  The previous heuristic was too complex with too many failure cases.
  You are thus assumed to want a given version asdf
  if and only if it is in your source-registry.

The general-purpose support code is now
a bit less than 50% of the code in ASDF.