Have depot_tools manpage generation pin asciidoc version too.

docs/src/make_docs.sh

 #!/bin/bash -e
 shopt -s nullglob
 
 cd $(dirname "$0")
 
 # Script which takes all the asciidoc git-*.txt files in this directory, renders
 # them to html + manpage format using git 1.9's doc toolchain, then puts
 # them in depot_tools to be committed.
 
 ensure_in_path() {
   local CMD=$1
   local PTH=$(which "$CMD")
   if [[ ! $PTH ]]
   then
     echo Must have "$CMD" on your PATH!
     exit 1
   else
     echo Using \'$PTH\' for ${CMD}.
   fi
 }
 
 ensure_in_path xmlto
-ensure_in_path asciidoc
 
 DFLT_CATALOG_PATH="/usr/local/etc/xml/catalog"
 if [[ ! $XML_CATALOG_FILES && -f "$DFLT_CATALOG_PATH" ]]
 then
   # Default if you install doctools with homebrew on mac
   export XML_CATALOG_FILES="$DFLT_CATALOG_PATH"
   echo Using \'$DFLT_CATALOG_PATH\' for \$XML_CATALOG_FILES.
 fi
 
+# We pull asciidoc to get the right version
+BRANCH=8.6.9
+ASCIIDOC_HASH=7fed0aff1b30
+if [[ ! -d asciidoc || $(cd asciidoc && hg id -i) != $ASCIIDOC_HASH ]]
+then
+  echo Cloning asciidoc
+  rm -rf asciidoc
+  hg clone -r $BRANCH https://asciidoc.googlecode.com/hg/ asciidoc
+  (cd asciidoc && ln -s asciidoc.py asciidoc)
+fi
+echo Asciidoc up to date at $ASCIIDOC_HASH \($BRANCH\)
+
+export PATH=`pwd`/asciidoc:$PATH
+
 # We pull git to get its documentation toolchain
 BRANCH=v1.9.0
 GITHASH=5f95c9f850b19b368c43ae399cc831b17a26a5ac
 if [[ ! -d git || $(git -C git rev-parse HEAD) != $GITHASH ]]
 then
   echo Cloning git
   rm -rf git
   git clone --single-branch --branch $BRANCH --depth 1 \
     https://kernel.googlesource.com/pub/scm/git/git.git  2> /dev/null
 
@@ skipping 141 matching lines @@
 do
   echo Copying ../man1/$x
   cp "git/Documentation/$x" ../man1
 done
 
 for x in "${MAN7_TARGETS[@]}"
 do
   echo Copying ../man7/$x
   cp "git/Documentation/$x" ../man7
 done