Fix wrapper script for branches with slahes

Use git-branch(1) instead of ls(1) for getting branch names.

hg2git.sh

@@ -67,7 +67,7 @@ rm -rf "$GIT_DIR/$PFX-$SFX_MARKS.old" "$GIT_DIR/$PFX-$SFX_MARKS.tmp"
 
 # save SHA1s of current heads for incremental imports
 # and connectivity (plus sanity checking)
-for head in `ls "$GIT_DIR/refs/heads"` ; do
+for head in `git branch | sed 's#^..##'` ; do
   id="`git-rev-parse $head`"
   echo ":$head $id"
 done > "$GIT_DIR/$PFX-$SFX_HEADS"