Adjust variable block applicability in dependency chains

Before the block used to apply to the set of prerequisites before the last
`:`. This turned out to be counterintuitive and not very useful since
prerequisite-specific variables are a lot less common than target specific.
And it doesn't fit with ad hoc recipes.

The new rule is if the chain ends with `:`, then the block applies to the last
set of prerequisites. Otherwise, it applies to the last set of targets. For
example:

./: exe{test}: cxx{main}
{
  test = true        # Applies to the exe{test} target.
}

./: exe{test}: libue{test}:
{
  bin.whole = false  # Applies to the libue{test} prerequisite.
}

This is actually consistent with both non-chain and non-block cases.
Consider:

exe{test}: cxx{main}
{
  test = true
}

exe{test}: libue{test}:
{
  bin.whole = false
}

exe{test}: libue{test}: bin.whole = false

The only exception we now have in this overall approach of "if the
dependency declaration ends with a colon, then what follows is for a
prerequisite" is for the first semicolon:

exe{test}:
{
  test = true
}

exe{test}: test = true

But that's probably intuitive enough since there cannot be a prerequisite
without a target.

1 files changed, 46 insertions, 0 deletions

diff --git a/tests/dependency/recipe/testscript b/tests/dependency/recipe/testscript
index bd33bcc..43ec514 100644
--- a/tests/dependency/recipe/testscript
+++ b/tests/dependency/recipe/testscript
@@ -139,6 +139,52 @@ EOI
   }}
 EOE
 
+: with-vars-depchain
+:
+$* <<EOI 2>>/~%EOE%
+./: alias{x}: alias{y}
+{
+  var = x
+}
+{{
+  echo
+}}
+dump alias{x}
+EOI
+<stdin>:8:1: dump:
+%  .+/alias\{x\}: .+/:alias\{y\}%
+  {
+    var = x
+  }
+  % [diag=echo] perform(update)
+  {{
+    echo
+  }}
+EOE
+
+: with-vars-replay-depchain
+:
+$* <<EOI 2>>/~%EOE%
+./: alias{x y}: alias{z}
+{
+  var = x
+}
+{{
+  echo
+}}
+dump alias{y}
+EOI
+<stdin>:8:1: dump:
+%  .+/alias\{y\}: .+/:alias\{z\}%
+  {
+    var = x
+  }
+  % [diag=echo] perform(update)
+  {{
+    echo
+  }}
+EOE
+
 : with-vars-header
 :
 $* <<EOI 2>>/~%EOE%