packaging: always pass VERSION into Inno invocation

The code in the Inno file was a holdover from before we had
Python driving execution.

With Python in the driver's seat, we can now have it resolve
the version string and pass it into Inno, making the code
easier to understand for people who aren't packaging gurus.

Differential Revision: https://phab.mercurial-scm.org/D7161

contrib/packaging/hgpackaging/inno.py

@@ -18,7 +18,10 b' from .py2exe import ('
     build_py2exe,
     stage_install,
 )
-from .util import find_vc_runtime_files
+from .util import (
+    find_vc_runtime_files,
+    read_version_py,
+)
 
 EXTRA_PACKAGES = {
     'dulwich',
@@ -149,7 +152,9 b' def build('
     if vc_x64:
         args.append('/dARCH=x64')
 
-    if version:
+    if not version:
+        version = read_version_py(source_dir)
+
         args.append('/dVERSION=%s' % version)
 
     args.append('/Odist')

contrib/packaging/hgpackaging/util.py

@@ -12,6 +12,7 b' import getpass'
 import glob
 import os
 import pathlib
+import re
 import shutil
 import subprocess
 import tarfile
@@ -210,3 +211,16 b' def process_install_rules('
             full_dest_path.parent.mkdir(parents=True, exist_ok=True)
             shutil.copy(full_source_path, full_dest_path)
             print('copying %s to %s' % (full_source_path, full_dest_path))
+
+
+def read_version_py(source_dir):
+    """Read the mercurial/__version__.py file to resolve the version string."""
+    p = source_dir / 'mercurial' / '__version__.py'
+
+    with p.open('r', encoding='utf-8') as fh:
+        m = re.search('version = b"([^"]+)"', fh.read(), re.MULTILINE)
+
+        if not m:
+            raise Exception('could not parse %s' % p)
+
+        return m.group(1)

contrib/packaging/inno/mercurial.iss

@@ -1,21 +1,6 b''
 ; Script generated by the Inno Setup Script Wizard.
 ; SEE THE DOCUMENTATION FOR DETAILS ON CREATING INNO SETUP SCRIPT FILES!
 
-#ifndef VERSION
-#define FileHandle
-#define FileLine
-#define VERSION = "unknown"
-#if FileHandle = FileOpen(SourcePath + "\..\..\mercurial\__version__.py")
-  #expr FileLine = FileRead(FileHandle)
-  #expr FileLine = FileRead(FileHandle)
-  #define VERSION = Copy(FileLine, Pos('"', FileLine)+1, Len(FileLine)-Pos('"', FileLine)-1)
-#endif
-#if FileHandle
-  #expr FileClose(FileHandle)
-#endif
-#pragma message "Detected Version: " + VERSION
-#endif
-
 #ifndef ARCH
 #define ARCH = "x86"
 #endif