git-gui dark theme patcher

darkize_git_gui.py

#!/bin/env python

import os
import subprocess
from sys import stderr

FORCED_GIT_GUI_PATH=None

# Do NOT modify anything below.
UNPATCHED_NEEDLE = 'pave_toplevel .'
PATCHED_NEEDLE_START = 'Dark theme: START'
PATCHED_NEEDLE_END = 'Dark theme: END'


def error_exit(msg: str) -> None:
    print(f"ERROR: {msg}", file=stderr)
    exit(1)


def check_access(filepath: str, mode: str):
   try:
      open(filepath, mode)
      return True

   except PermissionError:
      return False


def find_git_gui_path() -> str:
    result = subprocess.run(['git', '--exec-path'], capture_output=True, encoding='utf-8')
    if result.returncode != 0:
        error_exit(f"Couldn't find git exec path\n{result.stderr}")

    git_core_path = result.stdout.strip()
    return f'{git_core_path}/git-gui'


def patch_git_gui(path: bytes) -> None:
    with open(path, 'r') as f:
        lines = f.readlines()

    found_patched = False
    for i, line in enumerate(lines):
        if UNPATCHED_NEEDLE in line:
            start = i + 1
            break

        if PATCHED_NEEDLE_START in line:
            found_patched = True

    if found_patched:
        error_exit("Already patched with dark theme")

    lines.insert(start, THEME)
    print(''.join(lines))


THEME = f"""
# {PATCHED_NEEDLE_START}
ttk::style theme use default
ttk::style configure TFrame -background #333
ttk::style configure TLabelframe -background #333
ttk::style configure TLabelframe.Label -background #333 -foreground #fff
ttk::style configure TPanedwindow  -background #333
ttk::style configure EntryFrame -background #333
ttk::style configure TScrollbar -background #666 -troughcolor #444 -arrowcolor #fff -arrowsize 15
ttk::style map TScrollbar -background [list active #333 disabled #000]
ttk::style configure TLabel -background #333 -foreground #fff
ttk::style configure TButton -background #333 -foreground #fff -borderwidth 2 -bordercolor #fff
ttk::style map TButton -background [list active #555 disabled #111 readonly #000]
ttk::style configure TCheckbutton -background #333 -foreground #fff -indicatorbackground #666 -indicatorcolor #fff
ttk::style map TCheckbutton -background [list active #555 disabled #111 readonly #000]
ttk::style configure TEntry -fieldbackground #333 -background #333 -foreground #fff -insertcolor #fff
ttk::style configure TRadiobutton -background #333 -foreground #fff
ttk::style map TRadiobutton -background [list active #555 disabled #111 readonly #000]
option add *TCombobox*Listbox.background #333 interactive
option add *TCombobox*Listbox.foreground #fff interactive
option add *TCombobox*Listbox.selectBackground blue interactive
option add *TCombobox*Listbox.selectForeground #fff interactive
option add *Listbox.Background #333 interactive
option add *Listbox.Foreground #fff interactive
option add *Text.Background #333 interactive
option add *Text.Foreground #fff interactive
ttk::style configure TSpinbox -fieldbackground #333 -background #333 -foreground #fff -insertcolor #fff -arrowcolor #fff \\
    .vpane.lower.commarea.buffer.frame.t \\
    configure -background #0d1117 -foreground #fff -insertbackground #fff \\
    .vpane.lower.diff.body.t configure -background #0d1117 -foreground #fff \\
    .vpane.files.workdir.list configure -background #0d1117 -foreground #fff \\
    .vpane.files.index.list configure -background #0d1117 -foreground #fff \\
    .about_dialog.git_logo configure -background #333
# {PATCHED_NEEDLE_END}
"""

git_gui_path = FORCED_GIT_GUI_PATH or find_git_gui_path()
if not os.path.isfile(git_gui_path):
    error_exit(f"Cannot read file '{git_gui_path}'")

patch_git_gui(git_gui_path)