Add _tools folder for utility scripts

Add script to list unused images in the repository.

.gitignore

@@ -36,3 +36,7 @@ ehthumbs_vista.db
 $RECYCLE.BIN/
 logo.h
 *.autosave
+
+# Output of list-unused-images.sh tool
+tmp-unused-images
+tmp-unused-images-history

.travis.yml

@@ -24,10 +24,10 @@ install:
   - pip install codespell
 
 script:
-  - bash ./format.sh
+  - bash _tools/format.sh
 
   # Check for possible typos
-  - codespell -I codespell-ignore.txt {about,community,development,getting_started,tutorials}/**/*.rst
+  - codespell -I _tools/codespell-ignore.txt {about,community,development,getting_started,tutorials}/**/*.rst
 
   # TODO: Add `-W` to turn warnings into errors.
   # This can only be done once all warnings have been fixed.

_tools/list-unused-images.sh

@@ -0,0 +1,40 @@
+#!/bin/bash
+
+check_git_history=false
+
+rm -f tmp-unused-images
+rm -f tmp-unused-images-history
+
+# List images which might be unused.
+# Exceptions are ignored, and for .svg files we also look for potential .png
+# files with the same base name, as they might be sources.
+
+exceptions="docs_logo.png tween_cheatsheet.png"
+
+files=$(find -name "_build" -prune -o \( -name "*.png" -o -name "*.jpg" -o -name "*.svg" -o -name "*.gif" \) -print | sort)
+
+for path in $files; do
+  file=$(basename $path)
+  if echo "$exceptions" | grep -q "$file"; then
+    continue
+  fi
+  ext=${file##*.}
+  base=${file%.*}
+  found=$(rg -l ":: .*[ /]$file")
+  if [ -z "$found" -a "$ext" == "svg" ]; then
+    # May be source file.
+    found=$(rg -l ":: .*[ /]$base.png")
+  fi
+  if [ -z "$found" ]; then
+    echo "$path" >> tmp-unused-images
+  fi
+done
+
+
+if [ "$check_git_history" = true ]; then
+  for file in $(cat tmp-unused-images); do
+    echo "File: $file"
+    git log --diff-filter=A --follow $file
+    echo
+  done > tmp-unused-images-history
+fi