I typed out the first few characters of a changeset ID from Murky to pass to
hg diff. But I was surprised to get an 'unknown revision' error from Mercurial.
It seems that Mercurial treats changeset IDs as case-sensitive - so entering hexadecimal characters in upper case will not work. In light of this I think it would be best to display changeset IDs with lower case hexadecimal characters.