merge: store commitinfo if these is a dc or cd conflict delete-changed or changed-delete conflicts can either be resolved by mergetool, if some tool is passed and using or by user choose something on prompt or user doing some `hg revert` after choosing the file to remain conflicted. If the user decides to keep the changed side, on commit we just reuse the parent filenode. This is mostly fine unless we are in a distributed environment and people are doing criss-cross merges. Since, we don't have recursive merges or any other way of describing the end result of the merge was an explicit choice and it should be differentiated from it's ancestors, merge algo during criss-cross merges fails to take in account the explicit choice made by user and end up with a what-can-be-said-wrong-merge. The solution which we are trying to fix this is by creating a filenode on commit instead of reusing the parent filenode. This helps differentiate between pre-merged filenode and post-merge filenode and kind of tells about the choice user made. To implement creating new filenode functionality, we store info about these files in mergestate so that we can read them on commit and force create a new filenode. Differential Revision: https://phab.mercurial-scm.org/D8988

mergestate: update _stateextras instead of reassinging `merge.applyupdates()` can store extras for a file and _stateextras may not be empty always. Hence reassigning loses the old values. We can directly update like this because we switched to using `collections.defaultdict` for `_stateextras` sometime ago.

tests: add some debugmergestate calls in `test-merge-criss-cross.t` This will help notice the change in upcoming patches much better. Differential Revision: https://phab.mercurial-scm.org/D9028

tests: add few debugrevlogindex and a log call to see changes in next test In upcoming patches, we will create a new filenode in couple of cases. Let's add some debugrevlogindex and a log call so that we can observe those changes better. Differential Revision: https://phab.mercurial-scm.org/D8987

merge: disable `m2-vs-ma` optimization if new filenode config is true The `m2-vs-ma` optimization filters out the file which have not changed between second parent and the ancestor of the merge. This results in the m1-vs-m2 diff not processing those files. These files will be required when we are creating new filenode for salvaged cases as we need to track them to store in mergestate that file can be salvaged. Differential Revision: https://phab.mercurial-scm.org/D9027

configitems: add a new config option to control new filenode functionality This series is adding functionality where we can force create a new filenode for some files on a merge-commit. This is meant to represent an explicit choice made by user and hence distingusing the file in the merged commit with the file in parent by creating a new filenode instead of using the parent one. This introduces a experimental config option under which this functionality will be hidden. A new testcase is added in tests/test-merge-criss-cross.t to test the new functionality while making the option does not break other scenarios. Differential Revision: https://phab.mercurial-scm.org/D9026

git: add test showing `hg commit -i` working on a git repo Shows `hg commit -i` working on a git repo via the `git` extension. Adds working directory changes to files `alpha` and `beta`, then selects only `alpha` changes and commits them. As of now this would fail for a filename that includes uppercase characters due to the lack of case folding support in the extension. Differential Revision: https://phab.mercurial-scm.org/D9081