[isabelle-dev] NEWS: isabelle build options

[Makarius]

*** System ***

* Command-line tool "isabelle build" supports new options:
  - option -B NAME: include session NAME and all descendants
  - option -S: only observe changes of sources, not heap images


This refers to Isabelle/f7759beab4f2. The "system" manual contains more
explanations with some examples.


With "isabelle build -B Foo" it is possible to "focus" on session Foo,
e.g. after editing just that. All its descendants are selected for the
build process, but this implicitly includes its dependencies as usual.
This can often replace the undirected option -a in local tests.


With "isabelle build -S" we enter more ambitious reforms of the build
process: thus it becomes a hybrid of file-based vs. heap-based builds. A
typical application is "isabelle build -S -a", which even works after
deleting all heaps.

This also means we can continue the long-standing tradition (introduced
by Gerwin many years ago) to prefer parent heaps over repeated source
imports. In quick local tests heaps won't count with option -S, only the
sources that are actually imported.

Of course, a push requires a full test without that shortcut. E.g. a
proper re-build with all heaps could fail due to resource or timing
problems.


	Makarius