filemerge: clean up temp files in a finally block This isn't really a big deal because the temp files are created in $TMPDIR, but it makes some upcoming work simpler.

check-code: detect and ban 'util.Abort' We have seen the light, please use the new way.

error: get Abort from 'error' instead of 'util' The home of 'Abort' is 'error' not 'util' however, a lot of code seems to be confused about that and gives all the credit to 'util' instead of the hardworking 'error'. In a spirit of equity, we break the cycle of injustice and give back to 'error' the respect it deserves. And screw that 'util' poser. For great justice.

eol: rename 'error' to 'haserror' The variable 'error' conflict with the module name that we would like to import and use in a coming changeset.

discovery: rename 'error' to 'errormsg' The variable 'error' conflict with the module name that we would like to import and use in a coming changeset.

histedit: delete histedit statefile on any exception during abort When an user aborts a histedit, many things could go wrong. At a minimum, after a histedit abort failure, their repository should be out of that state. We've found situations where the user could not exit the histedit state without manually deleting the histedit state file. This patch ensures that if any exception happens during an abort, the histedit statefile will be deleted so that users are out of the histedit state and can at least manually get the repo back to a workable condition.

histedit: check presence of statefile before deleting it When the histeditstate class instance has it's clear() method called, there is nothing to check to see if the state file exists before deleting it. It may not exist, which would create an exception. This patch allows clear to be called at any time. This will be needed for the following patch.

histedit: add inprogress method to state class If a histedit is progress, the 'histedit-state' file should exist. The patch implements a convenience function to do check if a histedit is in progress. This method will be use in next patch in the series.

commands: use dirstateguard instead of begin/end-parentchange for backout Before this patch, "hg backout" uses 'begin'/'end'-'parentchange()' of 'dirstate' class to avoid writing incomplete dirstate changes out at failure. But this framework doesn't work as expected, if 'dirstate.write()' is invoked between them. In fact, in-memory dirstate changes may be written out at 'repo.status()' implied by 'merge.update()', even before this patch. To restore dirstate as expected at failure of "hg backout", this patch uses 'dirstateguard' instead of 'begin'/'end'-'parentchange()'.

commands: make "hg import" use dirstateguard only for --no-commit Previous patch made dirstate changes in a transaction scope "all or nothing". Therefore, 'dirstateguard' is meaningless, if its scope is as same as one of the related transaction. Before this patch, "hg import" uses 'dirstateguard' always, but transaction is also started if '--no-commit' isn't specified. To avoid redundancy, this patch makes "hg import" use dirstateguard only if transaction isn't started (= '--no-commit' is specified). In this patch, 'if dsguard' can be examined safely, because 'dsguard' is initialized (with None) before outermost 'try'.