Mercurial is great distributed version control system that we all use and love here at SPI.

If you're not familiar with distributed version control systems, the key thing to understand is that, unlike a central repository, Mercurial pulls all revisions to your local machine, so that you have the entire project history from day one.

This allows you to check-in / check-out / revert / branch all locally, without having to interface with a remote server repository until you're ready to push changes to the server.

Working on a Windows machine, with the server running on Linux/FreeBSD, introduces an interesting problem of "Case Folding Collision".

What is Case Folding Collision?

Linux/FreeBSD are case sensitive file systems. This means that hello.gif and HELLO.gif are two different files.

Windows on the other hand, is a case insensitive file system. You can't have both hello.gif and HELLO.gif in the same directory on a Windows machine.

Using Mercurial to pull/push between a Linux/FreeBSD and your local Windows machine, becomes problematic when you have multiple files with the same name different capitalization in the same folder.

Pulling changes from Mercurial aborts with an aggressive error, like


How to fix Mercurial Case Folding Collision

On the Linux/FreeBSD machine, we have to enter Mercurial "debug mode", go back to the bad version that introduced the files with same name different capitalization, delete them in that old revision and then go back to the current revision.

Here's how it's done:

Step 1: Enter Mercurial debug mode


The revision should be the one you are attempting to update to.


Step 2: Remove rogue files

Now we want to remove all the files in error.

You can use 'hg manifest tip' to check for the files in error.


Step 3: Commit changes


Step 4: Commit again (incase we had multiple heads)


Step 5: Go back to tip


Note: Often when dealing with case folding collision, you'll have more than one rogue file. Make sure you delete ALL of them on step 2, so that you don't have to repeat the process multiple times.

After you complete this process, make sure you remove the file from the local directory as well.


Otherwise it may get added again on the next commit

Hi Mike,

> Working on a Windows machine, with the server
> running on Linux/FreeBSD, introduces an
> interesting problem of "Case Folding Collision".

Note that this also occurs while working on a Windows XP machine, with the server running Windows XP.

Regards,
-- Nico-D