Implement default target statements

This introduces a new directive, the default target statement, which
may be used to control the list of targets built by default (i.e. if
no target is named on the command line).

1 files changed, 34 insertions, 6 deletions

diff --git a/doc/manual.asciidoc b/doc/manual.asciidoc
index bb120a5..112aac5 100644
--- a/doc/manual.asciidoc
+++ b/doc/manual.asciidoc
@@ -271,6 +271,30 @@ printed when run, logged (see below), nor do they contribute to the
 command count printed as part of the build process.
 
 
+Default target statements
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+By default, if no targets are specified on the command line, Ninja
+will build every output that is not named as an input elsewhere.
+You can override this behavior using a default target statement.
+A default target statement causes Ninja to build only a given subset
+of output files if none are specified on the command line.
+
+Default target statements begin with the `default` keyword, and have
+the format +default _targets_+.  A default target statement must appear
+after the build statement that declares the target as an output file.
+They are cumulative, so multiple statements may be used to extend
+the list of default targets.  For example:
+
+----------------
+default foo bar
+default baz
+----------------
+
+This causes Ninja to build the `foo`, `bar` and `baz` targets by
+default.
+
+
 The Ninja log
 ~~~~~~~~~~~~~
 
@@ -375,7 +399,9 @@ A file is a series of declarations.  A declaration can be one of:
 
 3. Variable declarations, which look like +_variable_ = _value_+.
 
-4. References to more files, which look like +subninja _path_+ or
+4. Default target statements, which look like +default _target1_ _target2_+.
+
+5. References to more files, which look like +subninja _path_+ or
    +include _path_+.  The difference between these is explained below
    <<ref_scope,in the discussion about scoping>>.
 
@@ -499,8 +525,9 @@ lookup order for a variable referenced in a rule is:
 Variable expansion
 ~~~~~~~~~~~~~~~~~~
 
-Variables are expanded in two cases: in the right side of a `name =
-value` statement and in paths in a `build` statement.
+Variables are expanded in three cases: in the right side of a `name =
+value` statement, in paths in a `build` statement and in paths in
+a `default` statement.
 
 When a `name = value` statement is evaluated, its right-hand side is
 expanded once (according to the above scoping rules) immediately, and
@@ -508,9 +535,10 @@ from then on `$name` expands to the static string as the result of the
 expansion.  It is never the case that you'll need to "double-escape" a
 variable with some syntax like `$$foo`.
 
-A `build` statement is first parsed as a space-separated list of
-filenames and then each name is expanded.  This means that spaces
-within a variable will result in spaces in the expanded filename.
+A `build` or `default` statement is first parsed as a space-separated
+list of filenames and then each name is expanded.  This means that
+spaces within a variable will result in spaces in the expanded
+filename.
 
 ----
 spaced = foo bar