The easy way

BryanOSullivan has created a Windows Mercurial package (see BinaryPackages) that is recommended for several reasons:

The hard way

To install Mercurial from sources under Windows, you need

If you are using [http://www.python.org python.org]'s Python, you will find that the [http://sourceforge.net/project/showfiles.php?group_id=78018&package_id=79063 win32 API extensions] make a huge performance difference when you use the clone command (but see the caveats below about hardlinks on Windows). If you are using Python 2.4, you will also need [http://starship.python.net/crew/mhammond/win32/Downloads.html mfc71.dll]. (These extensions are already shipped as part of [http://www.activestate.com/Products/ActivePython/ ActivePython], but ActivePython is not completely open source software.)

There is a file contrib/win32/win32-build.txt that comes with Mercurial that has instructions to build a Mercurial executable.

This pages describes some issues you may meet when trying to install Mercurial, and how to solve them.

Normally, you would only need to run 

python setup.py install --force

in the directory where you unpacked the sources, and everything would "just work". The use of -f/--force switch makes sure that any old installation is overwritten.

Where is my Mercurial?

By default, Mercurial (the executable) gets installed in a Scripts folder under your Python installation folder.

You can create a small batch file in a folder which is present in your path (e.g. your Windows installation folder) to help you launch Mercurial.

If you are running a Windows of the 9x series (Windows 95, 98 or ME), create a file called hg.bat with the following content: 

@echo off
shift
python <path-to-Scripts-folder>\hg %0 %1 %2 %3 %4 %5 %6 %7 %8 %9

For example, if you installed Python in c:\python, the content of the file would be 

@echo off
shift
python c:\python\hg %0 %1 %2 %3 %4 %5 %6 %7 %8 %9

Under Windows NT, create a file called hg.cmd with the following content: 

@python <path-to-Scripts-folder>\hg %*

For example, if you installed Python in c:\python, the content of the file would be 

@python c:\python\Scripts\hg %*

An alternative scheme that works better for some is to search for hg on the PATH. If you are using hg.exe it should work fine. For the python version of hg you should be able to simply rename 'hg' to 'hg.py' and assuming you have the .py extension configured it will be invoked. It is invoked, but there is a long standing redirection bug in Windows, and on XP there are sometimes problems with exit statuses being lost with this form of execution. So the following batch file is a solution -- place it in your PATH and it will find 'hg' without a .py extension in you PATH and invoke it properly: (name the file hg.cmd) 

@echo off
for /f %%i in ("hg") DO set HGSCRIPT="%%~$PATH:i"
if %HGSCRIPT% == "" (
        echo Cannot find hg on PATH
        exit /b 1
)
python %HGSCRIPT% %*

Python and MingW32

By default, Python and ActivePython will look for Microsoft Visual C to compile the extensions, so you have to tell setup.py to use the MingW32 compiler instead. You can do this by running 

python setup.py build --force -c mingw32
python setup.py install --force --skip-build

or more briefly: 

python setup.py build -f -c mingw32 install -f

If you are not familiar with mingw32, you will first need to download and install the following packages, in the order given: 

msys.exe
msysDTK.exe

Afterwards, download and install the following package, installing it in the directory where you installed the msys package (i.e. c:\msys\1.0\) 

MinGW.exe

You can find them at http://www.mingw.org

Then add the Python and mingw directories to your PATH, and run your build from the command prompt: 

set PATH=%PATH%;c:\python24;c:\msys\1.0\mingw\bin

Easier MingW32 based build via Cygwin

It is easier to install MinGW32 via Cygwin as it has a single graphical installer. After installing, mingw32 via Cygwin installer (setup.exe), add cygwin bin directory to the path and follow the mingw32 build instructions. e.g. 

set PATH=%PATH%;c:\python24;c:\cygwin\bin
python setup.py build --force -c mingw32
python setup.py install --force --skip-build

ActivePython and MS Visual C

If you are going to use MS Visual C, you may need to install an appropriate version of ActivePython:

A less than ideal work-around for the version check is to change your distutils notion of what version of MSVC Python was built with. Do this by editing your msvccompiler.py file in your python/Lib/distutils directory to match the version of MSVC you actually have, for example: 

   def __init__ (self, verbose=0, dry_run=0, force=0):
       CCompiler.__init__ (self, verbose, dry_run, force)
       self.__version = get_build_version()
 +     self.__version = 6 # override build version to match compiler

Other miscellaneous issues

WinZip7 does not seem to create empty files when extracting from .tar files. But WinZip9 is fine.

Using the SSH protocol

Two solutions:

Edit the Mercurial.ini to have the following entry: 

[ui]
ssh = C:\cygwin\bin\ssh.exe

Fix the path problem on Windows

If you try to use hg inside a directory that has a 'mercurial' subdirectory, for example when working on the mercurial sources, python may not be able to load the binary modules needed by Mercurial, and you may get a stack trace like: 

...
  File "C:\projects\hg\mercurial\demandload.py", line 54, in module
    return object.__getattribute__(self, 'importer').module()
  File "C:\projects\hg\mercurial\demandload.py", line 30, in module
    self.fromlist)
  File "C:\projects\hg\mercurial\mdiff.py", line 9, in ?
    import struct, bdiff, util, mpatch
ImportError: No module named bdiff

See the mail list thread "Fix the path problem on Windows..." but essentially Python on Windows ends up with the current directory automatically added to the python search path before the site libraries. So if you run hg in its own repository python gets confused, and can't find the extensions needed. There is a candidate patch that removes the current directory, but there is an arguably better workaround from K.Thananchayan. Simply add a registry entry (replacing 2.4 with the version of Python) 

 HKLM/SOFTWARE/Python/PythonCore/2.4/PythonPath/XXX
   (Default) REG_SZ "YYY"

Mercurial now includes support for cloning with hardlinks on Windows. However for this to work, your filesystem needs to support them (i.e. NTFS) and you need the win32 API extensions documented above. If you have a filesystem that does not support hardlinks or don't have the win32file module, mercurial clone will still work just fine - but you won't get the benefits of hardlinking of course.

For versions of Mercurial prior to 0.7, Mercurial won't realise that it has to 'break' hardlinks.

The upshot is that if you have repositories cloned with hardlinks you must not use pre-0.7 versions of mercurial on them (either the source or the destination clone), or use a version of python without win32file. If you do you are likely to get corruption.

A simple solution to break the hardlinks is to copy (using xcopy or File Explorer) one of the repositories, deleting the clone. Copying it back afterwards.

Default editor

The default editor for commit messages is 'vi'. The Windows installer creates a mercurial.ini that sets it to notepad. You can set the EDITOR (or HGEDITOR) environment variable to specify your preference or set it in mercurial.ini: 

[ui]
editor = whatever