Shorten the text used as a base for the CD VOLID if possible

Replace "alpha" with "a" and "beta" with "b". We've only got 32
characters to use here, so we need to shorten this. This way we can
specify DEBVERSION as a useful long string like "stretch-DI-alpha1" as
a version to appear in file/directory names, but without overflowing
at the VOLID level. May need more tweaks later here, but for now this
seems to do what we need.

FTAOD: this won't change "alpha" in the architecture name, as that is
added later.

debian/changelog

@@ -12,6 +12,8 @@ debian-cd (3.1.18) UNRELEASED; urgency=medium
     the code would only check sizes for packages explicitly listed but
     packages brought in due to dependency resolution would not be
     checked. Now fixed.
+  * Try to make VOLIDs shorter when given long alpha / beta release names
+    in DEBVERSION
 
   [ Didier Raboud ]
   * For stretch, swap amd64 and i386 to let the first be the norm, and the

tools/start_new_disc

@@ -36,6 +36,9 @@ if [ "$VOLID_BASE"x = ""x ] ; then
     VOLID_BASE="Debian $DEBVERSION"
 fi
 
+# Shorten the VOLID if we can - maximum length is 32 characters...
+VOLID_BASE=$(echo $VOLID_BASE | sed 's/alpha/a/gi;s/beta/b/gi;')
+
 if [ "$DISKINFO_DISTRO"x = ""x ] ; then
     DISKINFO_DISTRO="Debian"
 fi