Meta: Rewrite pre-commit script check-emoji in python

This reduces the scripts execution time from 0.57 seconds to 0.01
seconds, while also making the check a bit tighter, leaving fewer
possible problems.

Meta/check-emoji.py

@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+
+import os
+import re
+import sys
+
+RE_INVALID_CHAR = re.compile('[^A-FU0-9+_]')
+RE_MISSING_UNDERSCORE = re.compile('[^_]U')
+RE_MISSING_LETTER_U = re.compile('_(?!U)')
+RE_MISSING_SIGN_PLUS = re.compile('U(?!\\+)')
+
+
+def any_problems_here():
+    found_invalid_filenames = False
+    for filename in os.listdir():
+        if not filename.endswith('.png'):
+            print(f'Non-png file {filename} does not belong in the emoji directory')
+            found_invalid_filenames = True
+            break
+        filename = filename[:-len('.png')]
+        if RE_INVALID_CHAR.search(filename):
+            print(f'Filename {filename}.png contains invalid characters in its filename. Only uppercase letters'
+                  ' A-F and U, numbers, +, and _ should be used.')
+            found_invalid_filenames = True
+            break
+        if 'U+0' in filename:
+            print(f'Filename {filename}.png contains codepoint(s) with leading zeros. Leading zeros should be'
+                  ' removed from codepoint(s).')
+            found_invalid_filenames = True
+            break
+        if '+U' in filename:
+            print(f'Filename {filename}.png is incorrectly named. "_" should be used as a separator between'
+                  ' codepoints, not "+".')
+            found_invalid_filenames = True
+            break
+        if RE_MISSING_UNDERSCORE.search(filename):
+            print(f'Filename {filename}.png is missing an underscore "_" between codepoints.')
+            found_invalid_filenames = True
+            break
+        if RE_MISSING_LETTER_U.search(filename):
+            print(f'Filename {filename}.png is either missing a "U" to indicate the start of a codepoint,'
+                  ' or has a spurious underscore ("_").')
+            found_invalid_filenames = True
+            break
+        if RE_MISSING_SIGN_PLUS.search(filename):
+            print(f'Filename {filename}.png is either missing a "+" after a "U", or has a spurious "U".')
+            found_invalid_filenames = True
+            break
+        if 'U+FE0F' in filename:
+            print(f'Filename {filename}.png should not include any emoji presentation selectors. U+FE0F codepoints'
+                  ' should be removed from the filename.')
+            found_invalid_filenames = True
+            break
+
+    return found_invalid_filenames
+
+
+if __name__ == '__main__':
+    os.chdir(os.path.dirname(__file__) + "/../Base/res/emoji/")
+    if any_problems_here():
+        sys.exit(1)

Meta/lint-ci.sh

@@ -22,7 +22,7 @@ set +e
 for cmd in \
         Meta/check-ak-test-files.sh \
         Meta/check-debug-flags.sh \
-        Meta/check-emoji.sh \
+        Meta/check-emoji.py \
         Meta/check-markdown.sh \
         Meta/check-newlines-at-eof.py \
         Meta/check-png-sizes.sh \