effectflag: better diff detection Improve the diff detection algorithm to have less false positive like in the case of a rebase that move the hunk in the file but the hunk stays the same.

effectflag: add a test for content detection Add a test for diff detection when the diff is different but only because of line numbers. The test is a append at the end of the file and we try to rebase it. We shouldn't detect a content change, it will be done in the next patch.

test: fix test-evolve-effectflags dates Mercurial < 4.3 don't have default date so add globs in the test-metaedit.t file.