update-tags-encoding: escape '/' and ',' in tags

This is more conflict resistant than the old encoding where tags was a
file with a line per tag.

tools/update-tags-encoding

@@ -1,12 +1,7 @@
 #!/bin/bash
 #
-# Check out the specified branch (or `entomologist-data` if not specified)
+# Check out the `entomologist-data` branch in a temporary worktree.
-# in a temporary worktree.
+# For each issue with a `tags` file, replace the old-style tags file with a new-style tags dir.
-#
-# For each issue with a `tags` file:
-#
-#     replace the old-style tags file with a new-style tags dir
-#
 # git commit
 
 set -e