DVCS with a Windows central repository

Question

We are currently using VSS for version control. Quite few of our developers are interested in a distributed model (And want to get rid of VSS). Our network is full of Windows ma

Answer 1

After Benjamin pointed out the HTTP serving CGI scripts I decided to try those out and managed to get a repository hosted over HTTP. The Redbook which Benjamin linked was of much help as were two Mercurial wiki articles. One which describes Mercurial publishing in general and another containing step by step instructions for setting up the HgWebDir CGI script.

These instructions weren't completely foolproof though so I had to poke around a bit. Most likely as I'm running 64bit Vista. The instructions below document what I did. Now that I've done it once I'd probably do things in another order so don't consider these step by step instructions.

Mercurial

First I acquired the Mercurial binary from http://mercurial.berkwood.com/ which got installed into d:\dev\Mercurial. I created a repository for testing under d:\dev\testRepo repository using hg init. The d:\dev\Mercurial\library.zip contains Mercurial library files required by the CGI script so they were extracted to d:\dev\Mercurial\library. Something which confused me at first is that when I opened the zip file I received an error message and saw no contents. Just extracting the file to a directory worked though.

For the web script, I downloaded Mercurial source which contained the hgwebdir.cgi which got moved and renamed to d:\dev\Mercurial\webroot\hgwebdir.py. The step by step article contains good instructions for modifying the hgwebdir script for Windows. They also contain instructions for hgweb.config which in my case ended up looking like this:

[paths]
/hg/hgwebdir.py/test = D:\dev\Mercurial\testRepo

Also the repository wanted the following config so I could push there without SSL. Note I am using Basic Authentication to authenticate users currently. I had to create the config in D:\dev\Mercurial\testRepo\.hg\hgrc and add the following lines to it:

[web]
allow_push = *
push_ssl = false

Python

The CGI script is a Python script so it requires Python. It's seems pretty picky on which Python version executes it. One of the articles mentioned that running it requires same version that was used to build the Mercurial. In the end I got it working on Python 2.5 x86 after trying Python 2.6 x64, Python 2.4, Python 2.5 x64.

IIS

Two things I missed and had to install were CGI support and Basic Authentication. Both of these were installed through Control Panel, Programs and Features. Once done with installation I created a virtual directory (Which I later changed to an Application) in IIS pointing to D:\dev\Mercurial\webroot. The virtual directory required an CGI handler for *.py files which could be added from Handler Mappings. The executable was D:\dev\SDKs\Python25_x86\Python.exe %s. Once IIS had permissions to the webroot directory I could navigate to http://localhost/hg/hgwebdir.py/test and see the repository.

So now the read access was working. When I tried pushing to the repository I received weird error messages telling me it wasn't a real repository.

After an hour of debugging I ended up copying the whole D:\dev\Mercurial\library\mercurial tree under webroot so that Python could find D:\dev\Mercurial\webroot\mercurial\hgweb\hgwebdir_mod.pyc. After this Wireshark was reportting Access Denied errors in the stack trace. No idea what the real reason to this was but changing the virtual directory into an Application in IIS and moving it on top of an application pool which ran using Local System account the access denied errors went away.

Also at some point I gave HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinSock2\Parameters registry key more permissions so IIS could access it. Doubt that it requires these after using Local System account.

Once these were done pushing stuff to the repository using hg push http://localhost/hg/hgwebdir.cgi/test was working!

Problems and solutions

• Where to find the library files.
  • They were in the library.dll under Mercurial installation folder. I just had to extract them even if my unzip program refused to view me its contents.
• How to get the Python script to run
  • Download the correct Python version for x86 architecture as the script uses some x86 libraries. The correct Python version depends on the Mercurial version. For 1.2.1 it was Python 2.5 x86.
  • Alternatively you could try building Mercurial from sources with whatever Python version you want but in my case this failed when building extensions.
• How to set CGI up in IIS
  • First make sure CGI is installed in IIS. This wasn't assumed to be true in the IIS instructions Benjamin posted.
  • Create a new Module Mapping for *.py in IIS Handler Mappings. The correct Module is CgiModule and the executable is your Python executable + %s
• How to allow the CGI script to write to the repository
  • Make sure the script has everything it requires. I had to move the library\mercurial\hgweb\hgwebdir_mod.pyc to another place.
  • Make sure the script has permissions to everywhere it wants. I solved this by Creating a new Application Pool for the CGI script that used Local System account, converting the Virtual Directory to an Application in IIS and selecting the new Application Pool.