Merge branch 'bc/asciidoctor-tab-width'

Asciidoctor gives a reasonable imitation for AsciiDoc, but does not
render illustration in a literal block correctly when indented with
HT by default. The problem is fixed by forcing 8-space tabs.

* bc/asciidoctor-tab-width:
  Documentation: render revisions correctly under Asciidoctor
  Documentation: use 8-space tabs with Asciidoctor

Documentation/Makefile

@@ -185,7 +185,7 @@ ASCIIDOC = asciidoctor
 ASCIIDOC_CONF =
 ASCIIDOC_HTML = xhtml5
 ASCIIDOC_DOCBOOK = docbook45
-ASCIIDOC_EXTRA += -acompat-mode
+ASCIIDOC_EXTRA += -acompat-mode -atabsize=8
 ASCIIDOC_EXTRA += -I. -rasciidoctor-extensions
 ASCIIDOC_EXTRA += -alitdd='&\#x2d;&\#x2d;'
 DBLATEX_COMMON =

Documentation/revisions.txt

@@ -351,6 +351,7 @@ Here are a handful of examples using the Loeliger illustration above,
 with each step in the notation's expansion and selection carefully
 spelt out:
 
+....
    Args   Expanded arguments    Selected commits
    D                            G H D
    D F                          G H I J D F
@@ -373,3 +374,4 @@ spelt out:
 	  = B ^B^1 ^B^2 ^B^3
 	  = B ^D ^E ^F          B
    F^! D  = F ^I ^J D           G H D F
+....