Merged revisions 2136-2200,2202-2290,2292-2301 via svnmerge from

http://scons.tigris.org/svn/scons/branches/core

........
  r2145 | stevenknight | 2007-07-17 09:15:12 -0500 (Tue, 17 Jul 2007) | 3 lines

  Don't put null strings (from variable expansion) in a path list.
  (They get turned into the current directory on later expansion.)
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  r2146 | stevenknight | 2007-07-17 10:47:39 -0500 (Tue, 17 Jul 2007) | 3 lines

  Add support for optional arguments on command-line long options
  by specifying nargs='?'.
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  r2149 | stevenknight | 2007-07-17 15:22:24 -0500 (Tue, 17 Jul 2007) | 2 lines

  Remove left-over Optik mentions.
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  r2150 | stevenknight | 2007-07-17 15:39:34 -0500 (Tue, 17 Jul 2007) | 4 lines

  Add a $SWIGPATH variable for finding SWIG dependencies, with
  $SWIGINC{PREFIX,SUFFIX} for adding them to the command line.
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  r2154 | stevenknight | 2007-07-18 20:05:31 -0500 (Wed, 18 Jul 2007) | 2 lines

  Fix variable misspellings in the doc added for $SWIGOUTPUT.
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  r2155 | stevenknight | 2007-07-18 20:07:28 -0500 (Wed, 18 Jul 2007) | 2 lines

  Add the Python eggs info file to the RPM packaging build.
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  r2156 | stevenknight | 2007-07-18 20:15:08 -0500 (Wed, 18 Jul 2007) | 2 lines

  Convert documentation from DocBook SGML to XML.
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  r2158 | stevenknight | 2007-07-19 17:16:19 -0500 (Thu, 19 Jul 2007) | 3 lines

  Conditionally add the .egg-info the RPM file list only if the distutils
  in the version of Python that rpmbuild will execute knows about them.
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  r2161 | stevenknight | 2007-07-19 19:12:29 -0500 (Thu, 19 Jul 2007) | 5 lines

  Capture a test case (contributed by Tilo Prutz) where instantiation of
  a private class causes javac to generate an additional anonymous inner
  class file.  (No solution yet, but there's no sense throwing away the
  preparatory work.)
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  r2162 | stevenknight | 2007-07-20 11:29:56 -0500 (Fri, 20 Jul 2007) | 3 lines

  Support passing a list of .java files as source to the Java() builder.
  (Leanid Nazdrynau)
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  r2163 | garyo | 2007-07-20 12:00:35 -0500 (Fri, 20 Jul 2007) | 1 line

  Fixed cut-n-paste error in Touch factory method doc in users guide.
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  r2167 | stevenknight | 2007-07-21 22:59:40 -0500 (Sat, 21 Jul 2007) | 2 lines

  Don't execute the SWIGOUTDIR test if swig isn't installed.
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  r2168 | stevenknight | 2007-07-21 23:14:17 -0500 (Sat, 21 Jul 2007) | 2 lines

  Fix the test's ability to run under a path name containing spaces.
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  r2171 | stevenknight | 2007-07-24 15:54:41 -0500 (Tue, 24 Jul 2007) | 2 lines

  Handle white space in key file names in the packaging build.
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  r2172 | stevenknight | 2007-07-24 21:41:15 -0500 (Tue, 24 Jul 2007) | 2 lines

  More efficient copying of construction environments.
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  r2173 | stevenknight | 2007-07-25 10:56:02 -0500 (Wed, 25 Jul 2007) | 2 lines

  Update the SCons build for Subversion and general clean-up.
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  r2174 | stevenknight | 2007-07-25 11:35:16 -0500 (Wed, 25 Jul 2007) | 3 lines

  Suppress the [brackets] around a node in the --tree=prune output if
  the node is a source.
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  r2175 | stevenknight | 2007-07-25 12:52:18 -0500 (Wed, 25 Jul 2007) | 3 lines

  Commonize the skip_test() method and make its behavior configurable
  via a TESTCOMMON_PASS_SKIPS environment variable.
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  r2178 | stevenknight | 2007-07-25 21:43:47 -0500 (Wed, 25 Jul 2007) | 3 lines

  Add $JAVACLASSPATH and $JAVASOURCEPATH construction variables.  (Leanid
  Nazdrynau)
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  r2182 | stevenknight | 2007-07-30 12:10:20 -0500 (Mon, 30 Jul 2007) | 3 lines

  Refactor Builder suffix-adjusting into its own method, so we can
  (potentially) re-use it for Builders with attached source Builders.
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  r2183 | stevenknight | 2007-07-30 14:51:53 -0500 (Mon, 30 Jul 2007) | 2 lines

  More efficient source-builder suffix matching.
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  r2184 | stevenknight | 2007-07-30 16:01:42 -0500 (Mon, 30 Jul 2007) | 4 lines

  Encapsulate initialization of the default FS object by an accessor
  function in SCons.Node.FS.  (This also gets rid of an unnecessary
  reference to SCons.Node.FS.default_fs in the LaTeX scanner.)
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  r2193 | stevenknight | 2007-07-30 18:24:07 -0500 (Mon, 30 Jul 2007) | 3 lines

  Fix interpretation of source arguments that have no suffix when the
  called Builder has both a src_suffix and a src_builder.
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  r2194 | stevenknight | 2007-07-31 10:25:31 -0500 (Tue, 31 Jul 2007) | 2 lines

  Increase the number of tries for random output from three to ten.
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  r2195 | stevenknight | 2007-07-31 10:52:28 -0500 (Tue, 31 Jul 2007) | 3 lines

  Skip the test gracefully if the zipfile module can't read the file it
  just wrote (which is the case for Python 2.1 on 64-bit systems).
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  r2196 | stevenknight | 2007-07-31 13:06:21 -0500 (Tue, 31 Jul 2007) | 2 lines

  Move the "import zipfile" so it doesn't fail on Python <= 2.0.
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  r2197 | stevenknight | 2007-07-31 14:51:50 -0500 (Tue, 31 Jul 2007) | 3 lines

  Commonize initialization of the various Java builders so they can be
  hooked up into a multi-stage Builder chain.  (Leanid Nazdrynau)
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  r2198 | stevenknight | 2007-07-31 16:15:18 -0500 (Tue, 31 Jul 2007) | 3 lines

  Fix use of ${TARGET.dir} and ${SOURCE.dir} expansions in $FORTRANMODDIR
  $JARCHDIR, $JARFLAGS, $LEXFLAGS, $SWIGFLAGS, $SWIGOUTDIR and $YACCFLAGS.
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  r2199 | stevenknight | 2007-07-31 16:25:48 -0500 (Tue, 31 Jul 2007) | 2 lines

  Remove left-over Trace() call.
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  r2202 | stevenknight | 2007-08-01 12:31:48 -0500 (Wed, 01 Aug 2007) | 3 lines

  Bail out via test.skip_test() if wix ("candle") isn't found.
  Put the main body of code flush left instead of under an if: block.
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  r2203 | stevenknight | 2007-08-01 15:35:55 -0500 (Wed, 01 Aug 2007) | 5 lines

  Fix Tool.packaging.rpm.package() so it doesn't always overwrite
  $RPMFLAGS with -ta.
  Set --buildroot in RPM packaging tests so they don't overwrite
  each other when run simultaneously.
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  r2204 | stevenknight | 2007-08-01 15:37:36 -0500 (Wed, 01 Aug 2007) | 2 lines

  Fix a nested scope issue with the internal build_sources() function.
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  r2205 | stevenknight | 2007-08-01 15:46:08 -0500 (Wed, 01 Aug 2007) | 5 lines

  Normalize (X out) the CreationDate field inside embedded, compressed
  PostScript streams within the generated PDF files.  Also normalize
  preceding Length field, since compression length is affected by different
  patterns of input, including the variable CreationDate value.
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  r2211 | stevenknight | 2007-08-02 08:52:06 -0500 (Thu, 02 Aug 2007) | 2 lines

  Add the new modules from branches/packaging to the SCons packaging build.
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  r2212 | stevenknight | 2007-08-02 19:59:01 -0500 (Thu, 02 Aug 2007) | 2 lines

  Fix the JAVACLASSPATH test when javah isn't on the default $PATH.
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  r2214 | stevenknight | 2007-08-03 15:05:21 -0500 (Fri, 03 Aug 2007) | 4 lines

  Hook up the Java builders into a multi-step chain underneath a Java()
  pseudo-builder (wrapper) that examines its arguments and calls the
  appropriate underlying file-or-dir builder.
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  r2215 | stevenknight | 2007-08-03 15:49:58 -0500 (Fri, 03 Aug 2007) | 2 lines

  Fix for old Python versions:  use apply() instead of *args, **kw.
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  r2216 | stevenknight | 2007-08-03 16:49:31 -0500 (Fri, 03 Aug 2007) | 2 lines

  Hook up the SWIG builder as a source builder for .java files.
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  r2217 | stevenknight | 2007-08-03 17:28:19 -0500 (Fri, 03 Aug 2007) | 2 lines

  Don't use .endswith(), which didn't appear until later Python versions.
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  r2218 | stevenknight | 2007-08-03 17:29:38 -0500 (Fri, 03 Aug 2007) | 2 lines

  Replace tabs with spaces.
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  r2219 | stevenknight | 2007-08-04 08:06:23 -0500 (Sat, 04 Aug 2007) | 3 lines

  Initialize a loop-invariant lambda for matching .java suffixes outside
  the loop.
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  r2220 | stevenknight | 2007-08-07 15:06:13 -0500 (Tue, 07 Aug 2007) | 2 lines

  Refactor parallel class-generation loops into one.
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  r2221 | stevenknight | 2007-08-07 16:04:06 -0500 (Tue, 07 Aug 2007) | 5 lines

  Have the Java multi-step builder test actually check for generated files,
  and fix the generation of .java and .class file names, and interaction
  with the SWIG builder, so that the files are generated in the correct
  place.
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  r2222 | stevenknight | 2007-08-07 16:45:05 -0500 (Tue, 07 Aug 2007) | 3 lines

  Fix dependencies on SWIG-generated .java files so they don't have to
  be built in multiple passes.
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  r2226 | stevenknight | 2007-08-07 18:00:22 -0500 (Tue, 07 Aug 2007) | 2 lines

  Fix SWIG when used with BuildDir().
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  r2227 | stevenknight | 2007-08-07 22:15:55 -0500 (Tue, 07 Aug 2007) | 5 lines

  User's guide updates:
  - Make the multiple files example match its text.
  - Expand a truncated sentence about being able to use Python function actions
    in the Command() Builder.
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  r2228 | stevenknight | 2007-08-07 23:25:18 -0500 (Tue, 07 Aug 2007) | 3 lines

  Don't generate an error if a #include file matches a same-named
  directory in $CPPPATH (or $FORTRANPATH, etc.).
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  r2229 | stevenknight | 2007-08-07 23:40:00 -0500 (Tue, 07 Aug 2007) | 2 lines

  Fix a code example.  (Gary Oberbrunner)
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  r2230 | stevenknight | 2007-08-08 00:05:43 -0500 (Wed, 08 Aug 2007) | 3 lines

  Capture a test case to make sure AddPostAction() doesn't interfere
  with normal linking.  (Matt Doar, Gary Oberbrunner)
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  r2233 | stevenknight | 2007-08-08 14:15:44 -0500 (Wed, 08 Aug 2007) | 2 lines

  Fix documentation typo in a construction variable cross-reference.
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  r2234 | stevenknight | 2007-08-08 17:03:25 -0500 (Wed, 08 Aug 2007) | 2 lines

  Changes to SCons packaging to support checkpoint releases.
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  r2235 | stevenknight | 2007-08-09 10:10:01 -0500 (Thu, 09 Aug 2007) | 2 lines

  Sidestep false negatives on heavily loaded systems.
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  r2236 | garyo | 2007-08-09 11:16:26 -0500 (Thu, 09 Aug 2007) | 1 line

  Allow unpackaged files (e.g. *.pyo) to exist in the build dir without being packaged in the RPM.  Without this, on some systems the rpmbuild may error out.
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  r2237 | stevenknight | 2007-08-09 11:27:56 -0500 (Thu, 09 Aug 2007) | 5 lines

  Fix test/SWIG/build-dir.py so it works on old Python versions without
  distutils.sysconfig.
  Instead of just cutting-and-pasting initialization code from other
  SWIG tests, centralize it in some new TestSCons methods.
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  r2238 | garyo | 2007-08-09 11:30:58 -0500 (Thu, 09 Aug 2007) | 1 line

  Use docbook 4.3 instead of 4.4 for the XML doctype since some older(?) jade parsers can't handle new 4-byte Unicode chars in the 4.4 version of isogrk4.ent.
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  r2240 | stevenknight | 2007-08-09 16:35:06 -0500 (Thu, 09 Aug 2007) | 2 lines

  User's Guide updates (post packaging changes).
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  r2243 | stevenknight | 2007-08-10 10:31:51 -0500 (Fri, 10 Aug 2007) | 3 lines

  Fix the User's Guide build to use openjade, and to accomodate a change
  in the name of the main generated file (book1.html => index.html).
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  r2245 | stevenknight | 2007-08-10 11:09:16 -0500 (Fri, 10 Aug 2007) | 2 lines

  Update the {CHANGES,RELEASE}.txt datestamp lines.
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  r2253 | stevenknight | 2007-08-10 16:21:54 -0500 (Fri, 10 Aug 2007) | 2 lines

  Fix the wix Tool module's ability to handle null entries in $PATH.
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  r2261 | stevenknight | 2007-08-11 23:08:12 -0500 (Sat, 11 Aug 2007) | 3 lines

  Remove unnecessary files (.svnt/*, .{ae,cvs}ignore, www/*) from the
  scons-src packages.
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  r2262 | stevenknight | 2007-08-11 23:24:49 -0500 (Sat, 11 Aug 2007) | 2 lines

  Add missing __revision__ lines.
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  r2263 | stevenknight | 2007-08-11 23:33:42 -0500 (Sat, 11 Aug 2007) | 2 lines

  Skip the test if the MANIFEST file hasn't been built.
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  r2264 | stevenknight | 2007-08-11 23:36:30 -0500 (Sat, 11 Aug 2007) | 2 lines

  Add recent compatibility modules to the relevant exceptions lists.
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  r2265 | stevenknight | 2007-08-11 23:39:00 -0500 (Sat, 11 Aug 2007) | 3 lines

  Update __VERSION__ strings in the QMTest/*.py modules, so that packaging
  tests (src/test_*.py) will pass after builds of checkpoint releases.
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  r2266 | stevenknight | 2007-08-12 07:36:19 -0500 (Sun, 12 Aug 2007) | 2 lines

  Add a comment about why we construct the __VERSION__ string at run time.
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  r2267 | stevenknight | 2007-08-12 07:42:30 -0500 (Sun, 12 Aug 2007) | 2 lines

  Avoid reading the MANIFEST file twice.  (Courtesy review by Greg Noel.)
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  r2268 | stevenknight | 2007-08-12 08:14:53 -0500 (Sun, 12 Aug 2007) | 3 lines

  Shift Install() and InstallAs() from being documented as functions
  to being documented as Builders.
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  r2269 | garyo | 2007-08-13 08:49:52 -0500 (Mon, 13 Aug 2007) | 1 line

  Tests: Skip some more Java tests if javac is not installed on the test machine so they don't get marked as failing.
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  r2270 | garyo | 2007-08-13 11:09:39 -0500 (Mon, 13 Aug 2007) | 1 line

  Fixed typo in test (shows up on non-Linux platforms).
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  r2271 | garyo | 2007-08-13 14:09:05 -0500 (Mon, 13 Aug 2007) | 4 lines

  Test portability fixes for Darwin/OSX and IRIX.
  This does not make all the tests pass on those OSes,
  but it takes care of some of the more obvious errors that
  I have time for right now.  More to come.
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  r2272 | stevenknight | 2007-08-13 15:33:29 -0500 (Mon, 13 Aug 2007) | 2 lines

  Tab => space fix.
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  r2273 | stevenknight | 2007-08-13 15:33:52 -0500 (Mon, 13 Aug 2007) | 2 lines

  Test for swig, too, which is used to build from the .i file.
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  r2277 | garyo | 2007-08-14 10:40:00 -0500 (Tue, 14 Aug 2007) | 8 lines

  Test portability on IRIX: test/Actions/pre-post creates target file
  before building target, then IRIX CC does not chmod +x afterwards.
  I think this change is safe on all OSes.

  test/AS/ml.py: I think this is only supposed to be run on win32
  (not skipped only on win32); the sense of the skip test was backwards.
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  r2278 | stevenknight | 2007-08-14 11:04:40 -0500 (Tue, 14 Aug 2007) | 2 lines

  Add -tt when running tests, to catch inconsistent tab usage.
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  r2279 | stevenknight | 2007-08-14 14:00:43 -0500 (Tue, 14 Aug 2007) | 2 lines

  Minor refactor of logic in File.retrieve_from_cache().
........
  r2280 | stevenknight | 2007-08-15 01:11:40 -0500 (Wed, 15 Aug 2007) | 2 lines

  Refactor CacheDir support into its own module.
........
  r2281 | stevenknight | 2007-08-15 07:24:51 -0500 (Wed, 15 Aug 2007) | 2 lines

  Move the cachepath() method from FS.File to the CacheDir class.
........
  r2282 | stevenknight | 2007-08-15 08:31:34 -0500 (Wed, 15 Aug 2007) | 2 lines

  Python 1.5.2 fix in the new Null class.
........
  r2283 | stevenknight | 2007-08-15 10:45:53 -0500 (Wed, 15 Aug 2007) | 5 lines

  Refactor CacheDir unit tests to:
  - restore functionality that was dropped in the transition;
  - commonize creation of test Nodes and other (mock) objects
  - separate CacheDir tests from tests of CacheDir through Node.FS.File.
........
  r2284 | stevenknight | 2007-08-15 11:46:38 -0500 (Wed, 15 Aug 2007) | 3 lines

  Replace the Executor.Null.NullEnvironment object with a real Null object,
  so it will absorb the CacheDir method calls as well.
........
  r2285 | stevenknight | 2007-08-15 11:52:57 -0500 (Wed, 15 Aug 2007) | 5 lines

  Add a get_CacheDir() method to a construction environment, which will
  be used to fetch per-environment CacheDir specifications.  (Right now
  all calls to it still just return the one attached to underlying default
  FS object.)
........
  r2286 | stevenknight | 2007-08-15 15:15:46 -0500 (Wed, 15 Aug 2007) | 2 lines

  Support per-construction-environment configuration of CacheDir().
........
  r2287 | stevenknight | 2007-08-15 15:33:04 -0500 (Wed, 15 Aug 2007) | 2 lines

  Move the tests of CacheDir()-related command-line options into test/CacheDir.
........
  r2293 | stevenknight | 2007-08-16 11:14:49 -0500 (Thu, 16 Aug 2007) | 3 lines

  Add the Package() builder description to the documentation build,
  fixing the XML so that it will build.
........
  r2294 | stevenknight | 2007-08-16 12:51:19 -0500 (Thu, 16 Aug 2007) | 3 lines

  Reorganize packaging documentation:  alphabetize the variable definitions
  (and function names), document Tag() as a function, not a builder.
........
  r2296 | stevenknight | 2007-08-16 12:55:01 -0500 (Thu, 16 Aug 2007) | 2 lines

  Add a build command.
........
  r2300 | stevenknight | 2007-08-16 16:49:13 -0500 (Thu, 16 Aug 2007) | 2 lines

  First cut at documenting packaging variables.
........
  r2301 | stevenknight | 2007-08-16 16:51:21 -0500 (Thu, 16 Aug 2007) | 3 lines

  Construct the .src.rpm and .arch.rpm file names independnetly, not
  by trying to massage one into the other.
........

1 files changed, 240 insertions, 0 deletions

diff --git a/doc/user/actions.xml b/doc/user/actions.xml
new file mode 100644
index 0000000..928b7ea
--- /dev/null
+++ b/doc/user/actions.xml
@@ -0,0 +1,240 @@
+<!--
+
+  __COPYRIGHT__
+
+  Permission is hereby granted, free of charge, to any person obtaining
+  a copy of this software and associated documentation files (the
+  "Software"), to deal in the Software without restriction, including
+  without limitation the rights to use, copy, modify, merge, publish,
+  distribute, sublicense, and/or sell copies of the Software, and to
+  permit persons to whom the Software is furnished to do so, subject to
+  the following conditions:
+
+  The above copyright notice and this permission notice shall be included
+  in all copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+  KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+  WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+-->
+
+<!--
+
+=head1 Build actions
+
+Cons supports several types of B<build actions> that can be performed
+to construct one or more target files.  Usually, a build action is
+a construction command, that is, a command-line string that invokes
+an external command.  Cons can also execute Perl code embedded in a
+command-line string, and even supports an experimental ability to build
+a target file by executing a Perl code reference directly.
+
+A build action is usually specified as the value of a construction
+variable:
+
+  $env = new cons(
+	CCCOM         => '%CC %CFLAGS %_IFLAGS -c %< -o %>',
+	LINKCOM       => '[perl] &link_executable("%>", "%<")',
+	ARCOM         => sub { my($env, $target, @sources) = @_;
+				 # code to create an archive
+				}
+  );
+
+A build action may be associated directly with one or more target files
+via the C<Command> method; see below.
+
+=head2 Construction commands
+
+A construction command goes through expansion of construction variables
+and C<%-> pseudo-variables, as described above, to create the actual
+command line that Cons will execute to generate the target file or
+files.
+
+After substitution occurs, strings of white space are converted into
+single blanks, and leading and trailing white space is eliminated. It
+is therefore currently not possible to introduce variable length white
+space in strings passed into a command.
+
+If a multi-line command string is provided, the commands are executed
+sequentially. If any of the commands fails, then none of the rest are
+executed, and the target is not marked as updated, i.e. a new signature is
+not stored for the target.
+
+Normally, if all the commands succeed, and return a zero status (or whatever
+platform-specific indication of success is required), then a new signature
+is stored for the target. If a command erroneously reports success even
+after a failure, then Cons will assume that the target file created by that
+command is accurate and up-to-date.
+
+The first word of each command string, after expansion, is assumed to be an
+executable command looked up on the C<PATH> environment variable (which is,
+in turn, specified by the C<ENV> construction variable). If this command is
+found on the path, then the target will depend upon it: the command will
+therefore be automatically built, as necessary. It's possible to write
+multi-part commands to some shells, separated by semi-colons. Only the first
+command word will be depended upon, however, so if you write your command
+strings this way, you must either explicitly set up a dependency (with the
+C<Depends> method), or be sure that the command you are using is a system
+command which is expected to be available. If it isn't available, you will,
+of course, get an error.
+
+Cons normally prints a command before executing it.  This behavior is
+suppressed if the first character of the command is C<@>.  Note that
+you may need to separate the C<@> from the command name or escape it to
+prevent C<@cmd> from looking like an array to Perl quote operators that
+perform interpolation:
+
+  # The first command line is incorrect,
+  # because "@cp" looks like an array
+  # to the Perl qq// function.
+  # Use the second form instead.
+  Command $env 'foo', 'foo.in', qq(
+	@cp %< tempfile
+	@ cp tempfile %>
+  );
+
+If there are shell meta characters anywhere in the expanded command line,
+such as C<E<lt>>, C<E<gt>>, quotes, or semi-colon, then the command
+will actually be executed by invoking a shell. This means that a command
+such as:
+
+  cd foo
+
+alone will typically fail, since there is no command C<cd> on the path. But
+the command string:
+
+  cd $<:d; tar cf $>:f $<:f
+
+when expanded will still contain the shell meta character semi-colon, and a
+shell will be invoked to interpret the command. Since C<cd> is interpreted
+by this sub-shell, the command will execute as expected.
+
+=head2 Perl expressions
+
+If any command (even one within a multi-line command) begins with
+C<[perl]>, the remainder of that command line will be evaluated by the
+running Perl instead of being forked by the shell.  If an error occurs
+in parsing the Perl code, or if the Perl expression returns 0 or undef,
+the command will be considered to have failed.  For example, here is a
+simple command which creates a file C<foo> directly from Perl:
+
+  $env = new cons();
+  Command $env 'foo',
+    qq([perl] open(FOO,'>foo');print FOO "hi\\n"; close(FOO); 1);
+
+Note that when the command is executed, you are in the same package as
+when the F<Construct> or F<Conscript> file was read, so you can call
+Perl functions you've defined in the same F<Construct> or F<Conscript>
+file in which the C<Command> appears:
+
+  $env = new cons();
+  sub create_file {
+	my $file = shift;
+	open(FILE, ">$file");
+	print FILE "hi\n";
+	close(FILE);
+	return 1;
+  }
+  Command $env 'foo', "[perl] &create_file('%>')";
+
+The Perl string will be used to generate the signature for the derived
+file, so if you change the string, the file will be rebuilt.  The contents
+of any subroutines you call, however, are not part of the signature,
+so if you modify a called subroutine such as C<create_file> above,
+the target will I<not> be rebuilt.  Caveat user.
+
+=head2 Perl code references [EXPERIMENTAL]
+
+Cons supports the ability to create a derived file by directly executing
+a Perl code reference.  This feature is considered EXPERIMENTAL and
+subject to change in the future.
+
+A code reference may either be a named subroutine referenced by the
+usual C<\&> syntax:
+
+  sub build_output {
+	my($env, $target, @sources) = @_;
+	print "build_output building $target\n";
+	open(OUT, ">$target");
+	foreach $src (@sources) {
+	    if (! open(IN, "<$src")) {
+		print STDERR "cannot open '$src': $!\n";
+		return undef;
+	    }
+	    print OUT, <IN>;
+	}
+	close(OUT);
+	return 1;
+  }
+  Command $env 'output', \&build_output;
+
+or the code reference may be an anonymous subroutine:
+
+  Command $env 'output', sub {
+	my($env, $target, @sources) = @_;
+	print "building $target\n";
+	open(FILE, ">$target");
+	print FILE "hello\n";
+	close(FILE);
+	return 1;
+  };
+
+To build the target file, the referenced subroutine is passed, in order:
+the construction environment used to generate the target; the path
+name of the target itself; and the path names of all the source files
+necessary to build the target file.
+
+The code reference is expected to generate the target file, of course,
+but may manipulate the source and target files in any way it chooses.
+The code reference must return a false value (C<undef> or C<0>) if
+the build of the file failed.  Any true value indicates a successful
+build of the target.
+
+Building target files using code references is considered EXPERIMENTAL
+due to the following current limitations:
+
+=over 4
+
+Cons does I<not> print anything to indicate the code reference is being
+called to build the file.  The only way to give the user any indication
+is to have the code reference explicitly print some sort of "building"
+message, as in the above examples.
+
+Cons does not generate any signatures for code references, so if the
+code in the reference changes, the target will I<not> be rebuilt.
+
+Cons has no public method to allow a code reference to extract
+construction variables.  This would be good to allow generalization of
+code references based on the current construction environment, but would
+also complicate the problem of generating meaningful signatures for code
+references.
+
+=back
+
+Support for building targets via code references has been released in
+this version to encourage experimentation and the seeking of possible
+solutions to the above limitations.
+
+-->
+
+ <para>
+
+   XXX
+
+ </para>
+
+ <section>
+ <title>XXX</title>
+
+   <para>
+
+   XXX
+
+   </para>
+
+ </section>