Add changelog and tweak in preparation of PxTP

.gitignore

-_minted-doc/
-_minted-comments/
+_minted-*/
 *.aux
 *.bbl
 *.blg
@@ -10,3 +9,4 @@ _minted-comments/
 *.pdf
 *.pag
 *.toc
+*.pyg

spec/changelog.tex

+%\subsection*{Unreleased}
+
+\subsection*{0.1 --- \DTMdisplaydate{2021}{07}{10}{-1}}
+
+This is the first public release of this document.  It coincides with
+the seventh PxTP Workshop.

spec/version.sh

@@ -3,8 +3,8 @@
 
 v=`git describe --tag --dirty=-changed --always 2> /dev/null`
 if [ -n "$v" ]; then
-    printf "git revision %s." "$v"
+    printf "%s" "$v"
 else
-	echo "an unknown git revision."
+	echo "not known"
 fi