How to solve a Mercurial case-folding collision?

Question

I use Mercurial as source control with the main repository managed on KILN. At one point in time I changed my iOS project name from WeatherTimeMachine to weathertimemachine. This resulted in a case change of several files and folders:

• WeatherTimeMachine.xcode
• WeatherTimeMachine_Prefix.pch
• WeatherTimeMachine-Info.plist

In the meantime I've added a tag to a revision in KILN... So I now have:

• a head in KILN
• a head on my local repo with case changes

When trying to merge I get the following error message: "Mercurial case-folding collision"

How can I fix this?

Answer 1

If you're on Mac OS X, you don't need to export your repository to Linux or another foreign case-sensitive file system as suggested by the Mercurial documentation. Just use Disk Utility to create a case-sensitive, journaled disk image slightly bigger than your repository, copy your repo there, then remove the conflicting files and commit.

Answer 2

I have found some information here: FixingCaseCollisions, but somehow this did not work for me. Here is how I managed to solve this issue:

Make a copy of your existing repository folder (for safety). For example:

• cp -r WeatherTimeMachine WeatherTimeMachineCopy

Fool mercurial into thinking the problematic revision is the current tip:

• hg debugsetparents <bad revision>
• hg debugrebuildstate

Remove the files which are causing the problem (-f is required to force the removal). Here is an example:

• hg rm -A -f WeatherTimeMachine-Info.plist

Once all problematic files have been removed, commit the changes

• hg ci -m "fixed collision-folding issue" -u michael

Then restore mercurial to the proper revision

• hg debugsetparents tip
• hg debugrebuildstate

After this the merge is possible and the problem is gone.

And now I can happily resume working with MacHg to manage my Mercurial repository and push my change sets to KILN.

Answer 3

This is a no-programming no-hg answer, but it solved my mercurial case-folding problems once and for all! For now anyway..

I gave up trying to avoid and "fix" the case-collision problems. That just looks ugly and you can never really "solve" the problem, only can do a workaround.

The only way (that I can think of) to really solve the problem is to have a case-sensitive filesystem. No need to reformat your entire disk, a single partition will do the job nicely.

I used the Disk Utility app that comes with the os, pretty straightforward, just remember to select Mac OS Extended (Case-sensitive, Journaled) when creating new partition. Also, note that the Disk Utility can resize partitions only by moving the end (not the beginning) of partition.

You can probably create a symlink to where your old source code lived, so no need to change the IDE settings and stuff (but I haven't tried this, just happy with the new partition).

Answer 4

We resolved this without resorting to a case-sensitive filesystem by issuing HG rename commands. Say you are having trouble because "Foo.txt" needs to be called "foo.txt":

> hg rename Foo.txt Foo.txt.renamed
> hg rename Foo.txt.renamed foo.txt

We encountered this problem when a file was deleted and then later re-created in the main repository with the same name, but different case. A branch repository that was created before these changes could not then be merged in, despite the changesets from the main repository having been pulled.