I have a repo with a XML file which contains 46K symbols arranged in one line without any CR/LFs. When user makes a change in this file and then tries to commit the changes with TortioseHg, thg hangs. Thg version 2.6.1 x64. If user commits the change using hg commit in console, TortoiseHg hangs when user clicks on this revision.
Probably there is some problem with displaying very long lines in diffs.
One may reproduce the problem using the attached file. Create a repo, add the file to it, and try to change and commit.