the preproc should be a unix filter

README

@@ -71,8 +71,8 @@ fugitive README file
 </p>
 <p>
   If you want your article to be preprocessed by an external tool (markdown,
-  textile...) you need to set <em>preproc</em> to a command line that will take
-  the file path as argument and write to stdout.
+  textile...) you need to set <em>preproc</em> to a command line that will read
+  on stdin and write to stdout.
 </p>
 
 <h2>Usage</h2>

post-commit.sh

@@ -197,7 +197,7 @@ for f in $added_files $new $modified_files; do
     if [ "$preproc" != "" ]; then
       preproc_bak=`tempfile -p "fugitive" -d "$articles_dir"`
       mv "$f" "$preproc_bak"
-      $preproc "$preproc_bak" > "$f"
+      ($preproc) < "$preproc_bak" > "$f"
     fi
     art="${f#$articles_dir/}"
     echo -n "[fugitive] Generating $public_dir/$art.html from $f... "