inno: script to automate building Inno installer The official Inno installer build process is poorly documented. And attempting to reproduce behavior of the installer uploaded to www.mercurial-scm.org has revealed a number of unexpected behaviors. This commit attempts to improve the state of reproducibility of the Inno installer by introducing a Python script to largely automate the building of the installer. The new script (which must be run from an environment with the Visual C++ environment configured) takes care of producing an Inno installer. When run from a fresh Mercurial source checkout with all the proper system dependencies (the VC++ toolchain, Windows 10 SDK, and Inno tools) installed, it "just works." The script takes care of downloading all the Python dependencies in a secure manner and manages the build environment for you. You don't need any additional config files: just launch the script, pointing it at an existing Python and ISCC binary and it takes care of the rest. The produced installer creates a Mercurial installation with a handful of differences from the existing 4.9 installers (produced by someone else): * add_path.exe is missing (this was removed a few changesets ago) * The set of api-ms-win-core-* DLLs is different (I suspect this is due to me using a different UCRT / Windows version). * kernelbase.dll and msasn1.dll are missing. * There are a different set of .pyc files for dulwich, keyring, and pygments due to us using the latest versions of each. * We include Tcl/Tk DLLs and .pyc files (I'm not sure why these are missing from the existing installers). * We include the urllib3 and win32ctypes packages (which are dependencies of dulwich and pywin32, respectively). I'm not sure why these aren't present in the existing installers. * We include a different set of files for the distutils package. I'm not sure why. But it should be harmless. * We include the docutils package (it is getting picked up as a dependency somehow). I think this is fine. * We include a copy of argparse.pyc. I'm not sure why this was missing from existing installers. * We don't have a copy of sqlite3/dump.pyc. I'm not sure why. The SQLite C extension code only imports this module when conn.iterdump() is called. It should be safe to omit. * We include files in the email.test and test packages. The set of files is small and their presence should be harmless. The new script and support code is written in Python 3 because it is brand new and independent code and I don't believe new Python projects should be using Python 2 in 2019 if they have a choice about it. The readme.txt file has been renamed to readme.rst and overhauled to reflect the existence of build.py. Differential Revision: https://phab.mercurial-scm.org/D6066