Fix bugs and modernize new_beamer_presentation script

Switch from git checkout-index to git archive with a temp directory,
fixing unquoted variables, TMPDIR name collision, missing set -e,
missing existence check for destination, and mktemp running
unconditionally. Fix typo in error message.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

slides_template/new_beamer_presentation

@@ -4,37 +4,40 @@
 # Copyright (c) 2009-2022 Benjamin Mako Hill <mako@atdot.cc>
 # Released under the GPLv3 or later.
 
+set -e
+
 SOURCEDIR="$HOME/tex/beamer-mako"
-CURDIR=`pwd`
+CURDIR=$(pwd)
 
-if test $1
+if [ -n "$1" ]
 then
-    cd $SOURCEDIR
-    git checkout-index -f --prefix=$CURDIR/$1/ $(find template -not -type d)
-    cd $CURDIR
+    if [ -e "$1" ]; then
+        echo "error: '$1' already exists"
+        exit 1
+    fi
 
-    # get rid of paper_template subdir
-    mv $1/template/* $1
-    mv $1/template/.gitignore $1
-    rm -rf $CURDIR/$1/template
+    WORK_DIR=$(mktemp -d)
+    cd "$SOURCEDIR"
+    git archive --format=tar HEAD template | tar x --strip=1 -C "$WORK_DIR"
+    cd "$CURDIR"
+    mv "$WORK_DIR" "$1"
 
-    mv $1/example.tex $1/$1.tex
+    mv "$1/example.tex" "$1/$(basename "$1").tex"
 
     # create a symlink farm for the fonts
-    # rm -rf "./fonts/*"
-    cd $1
+    cd "$1"
     rm -rf ./fonts/*
 
-    # first created the directories
+    # first create the directories
     for fontdir in "${SOURCEDIR}/template/fonts/"*; do
         mkdir "./fonts/$(basename "${fontdir}")"
         # then the files
         for fontfile in "${fontdir}/"*; do
             ln -s "${fontfile}" "./fonts/$(basename "${fontdir}")/$(basename "${fontfile}")"
-        done;
-    done;
+        done
+    done
 
-    cd $CURDIR
+    cd "$CURDIR"
 else
-    echo "specifiy a directory where the template should go";
+    echo "specify a directory where the template should go"
 fi