histedit: preserve initial author on fold (issue4296) When the authorship of the changeset folded in does not match that of the base changeset, we currently use the configured ui.username instead. This is especially surprising when the user is not the author of either of the changesets. In such cases, the resulting authorship (the user's) is clearly incorrect. Even when the user is folding in a patch they authored themselves, it's not clear whether they should take over the authorship. Let's instead keep it simple and always preserve the base changeset's authorship. This is also how "git rebase -i" handles folding/squashing.

run-tests: fix some io ordering backported from default

merge with stable

test-revert: add case where file is tracked but deleted in working directory

test-revert: add case with untracked files with unique content This test highlights similar misbehavior as its parent changesets.

test-revert: add case with untracked files with reverted content This test highlights similar misbehaviors as its parent changesets.

test-revert: add case where file exists but is untracked in working directory This test highlights a small misbehavior in output when reverting to another revision not including the untracked file.