config/NEWS.md

# 0.NEXT.0: Sometime

 - the *serialization format has changed* to one that's extensible
   and lets the library evolve without breaking serialization all
   the time. The new format is also much more compact. However,
   this change is incompatible with old serializations, if you
   rely on that. The hope is to avoid serialization breakage in
   the future now that the format is not the default Java one
   (which was a direct dump of all the implementation details).
 - *serializing an unresolved Config* (one that hasn't had
   resolve() called on it) is no longer supported, you will get
   NotSerializableException if you try.
 - ConfigValue.render() now supports ConfigRenderOptions which
   means you can get a *no-whitespace no-comments plain JSON
   rendering* of a ConfigValue
 - supports *self-referential substitutions*, such as
   `path=${path}":/bin"`, by "looking backward" to the previous
   value of `path`
 - supports *concatenating arrays and merging objects within a
   single value*. So you can do `path=${path} [ "/bin" ]` for
   example. See README and spec for more details.
 - supports *array append* `+=` where `path+="/bin"` expands to
   `path=${?path} [ "/bin" ]`
 - supports *specifying type of include* `include
   url("http://example.com/")`, `include file("/my/file.conf")`,
   and `include classpath("whatever")`.  This syntax forces
   treatment as URL, file, or classpath resource.
 - supports *including URLs* `include
   "http://example.com/whatever.conf"` (if an include is a valid
   URL, it's loaded as such). This is incompatible with prior
   versions, if you have a filename that is also a valid URL, it
   would have loaded previously but now it will not. Use the
   `include file("")` syntax to force treatment as a file.
 - *class loaders are now recursively inherited* through include
   statements; previously, even if you set a custom class loader
   when parsing a file, it would not be used for parsing a
   classpath resource included from the file.
 - parseString() and parseReader() now support include statements
   in the parsed string or reader
 - in -Dconfig.resource=name, name can start with a "/" or not,
   doesn't matter
 - if you implement ConfigIncluder, you should most likely also
   implement ConfigIncluderFile, ConfigIncluderURL, and
   ConfigIncluderClasspath. You should also use
   ConfigIncludeContext.parseOptions() if appropriate.
 - cycles in include statements (self-includes) are now detected
   and result in a nicer error instead of stack overflow
 - since 0.3.0, there is an obscure incompatible semantic change
   in that self-referential substitutions where the cycle could
   be broken by partially resolving the object now "look backward"
   and may fail to resolve. This is not incompatible with the
   version included in Play/Akka 2.0 because in that version this
   obscure case just threw an exception. But in 0.3.0 there
   were cases that worked that now work differently. You are very
   unlikely to be affected by this.

# 0.3.0: March 1, 2012

 - ConfigFactory methods now use the thread's context class loader
   by default, and have overloads so you can specify a class
   loader. Because jars may come with "reference.conf" in the jar,
   a config must always be loaded with the same class loader as
   the jar using the config.
 - ConfigValue instances are now serializable
 - new methods ConfigObject.withoutKey, ConfigObject.withOnlyKey,
   Config.withoutPath, Config.withOnlyPath allow subsetting
   configs more easily.
 - better handle complex interdependent substitutions (the
   `${foo}` syntax) without getting confused; just about anything
   that makes conceptual sense should now work. Only inherently
   circular config files should fail.
 - some minor documentation fixes.