Changes to get Beginners booke building.

The web pages include prev and next links, so to get those right we
have to make the tune filenames distinct from the main booke names.
So fall back to taking the easy way, and just prefix all tune names with
@ or _.

abcfield.py

@@ -189,6 +189,10 @@ def expandCustomMarkdown(t, dir):
     def getTitleLink(m):
         fname = m.group(1) + ".abc"
         path = pathlib.Path(dir, fname)
+        if not path.exists():
+            path = pathlib.Path(dir, '@' + fname)
+        if not path.exists():
+            path = pathlib.Path(dir, '_' + fname)
         with path.open() as f:
             lines = f.readlines()
             return "[" + getFullTitle(lines, dir) + "](" + fname + ")"

makeGraphics.sh

@@ -22,6 +22,11 @@ find $booke -maxdepth 1 -name "*.abc" |
     do
         name=`basename $filename .abc`
 
+        # Already generated?
+        if [ -f $graphicsdir/${name}.pdf ]; then
+            continue
+        fi
+
         # Make the tune graphic.
         abcm2ps -E -F singletune -O $graphicsdir/$name.eps $filename
         # Make $name.eps so we can build with LaTeX.
@@ -53,6 +58,11 @@ find ${booke}/Compact -maxdepth 1 -name "*.abc" |
     do
         name=`basename $filename .abc`
 
+        # Already generated?
+        if [ -f $graphicsdir/compact-${name}.pdf ]; then
+            continue
+        fi
+
         # Make the tune graphic.
         abcm2ps -E -F singletune -O $graphicsdir/compact-${name}.eps $filename
         # Make $name.eps so we can build with LaTeX.

makeWebAudio.sh

@@ -78,6 +78,12 @@ find $booke -maxdepth 1 -name "*.abc" | sort |
     do
         name=`basename $filename .abc`
         tunedir=$basetunedir/$name
+
+        # Already generated?
+        if [ -f $tunedir/${name}.mp3 ]; then
+            continue
+        fi
+
         mkdir -p $tunedir
 
         makeaudiofiles $filename $tunedir

makeWebGraphics.sh

@@ -29,6 +29,12 @@ find $booke -maxdepth 1 -name "*.abc" | sort |
     do
         name=`basename $filename .abc`
         tunedir=$basetunedir/$name
+
+        # Already generated?
+        if [ -f $tunedir/${name}.pdf ]; then
+            continue
+        fi
+
         mkdir -p $tunedir
 
         tmpname=${name}.tmp