What does the equal sign mean in TortoiseMerge?

Going off of the documentation reference given by Randy D. Binondo and prior experience with VCSs, it appears to mean that the line change would have been made with a full merge, but was automatically reverted for some reason (e.g., when merging a limited set of revisions from a branch rather than all revisions).

This makes sense since the prior revisions may be required in order for Subversion to build a proper diff for the merge. I strongly suspect that Subversion compiles all diffs for each relevant branch starting from the revisions' common ancestor and then attempts to revert the undesired diffs, leading to the behavior which is indicated by the equals-sign symbol. I've yet to read the Version Control with Subversion book, but that may provide more insight to this as well.

The symbol certainly does not mean that both files made the same changes independently, as Phonon suggested. A quick test proves this.

Mike's answer is correct. To elaborate a bit, this is an artifact of the way subversion merges changes. It applies all changes that occurred between the merge source and destination, regardless of which changes you told it to merge, and then "undoes" any changes that you didn't specify.

Here's an example: I branch a file from my trunk at rev 1. I change line 100 in my trunk version and commit it as rev 2. Then I change line 200 and commit that as rev 3. If I then go to merge only rev 3 into my branch, I will see one of these equals symbols at line 100 because subversion merged rev 2, merged rev 3, and then un-merged rev 2. Since the user specified only to merge the changes in rev 3, the change in rev 2 is NOT included in the merge.

I'm pretty sure this means that both files made identical changes independently.

With reference to tortoise's docs, it means "A change has been undone by reverting to the original content of the line."

Line Status Icons Chapter 3. Using TortoiseMerge

http://tortoisesvn.net/docs/nightly/TortoiseMerge_en/tmerge-dug-icons.html