mergestate: use _stateextras instead of merge records for commit related info There is a set of information related to a merge which is needed on commit. We want to store such information in the mergestate so that we can read it while committing. For this purpose, we are using merge records and introduced a merge entry state for that. However this won't scale and is not clean way to implement this. This patch reworks the existing logic related to this to use _stateextras and read from it. Right now the information stored is not very descriptive but it will be in next patch. Using _stateextras also makes MERGE_RECORD_MERGED_OTHER useless and only to be kept for BC. Differential Revision: https://phab.mercurial-scm.org/D8920

mergestate: use collections.defaultdict(dict) for _stateextras I want to use this _stateextras more in upcoming patches to store some commit time related information. Using defaultdict will help in cleaner code around checking whether a file exists or not. Differential Revision: https://phab.mercurial-scm.org/D8919

hgweb: minimize scope of a try-block in staticfile() I think the exceptions are only relevant for the `os.stat()` and `open()` calls, and maybe to the `fh.read()` call. Differential Revision: https://phab.mercurial-scm.org/D8936

hgweb: ignore web.templates config when guessing mime type for static content Frozen binaries won't have a file-system path for static content, so I'd like to remove dependence on that. From the documentation, it seems like `mimetypes.guess_type()` only cares about the suffix, so I think it should be enough to pass in just path under the `web.templates` directory. Differential Revision: https://phab.mercurial-scm.org/D8935

hgweb: let staticfile() look up path from default location unless provided This reduces duplication between the two callers. Differential Revision: https://phab.mercurial-scm.org/D8934

hgweb: handle None from templatedir() equally bad in webcommands.py The following paragraph is based just on my reading of the code; I have not tried to test it. Before my recent work on templates in frozen binaries, it seems both `hgwebdir_mod.py` and `webcommands.py` would pass in an empty list into `staticfile()` when running in a frozen binary. That would then result in a variable in that function (`path`) not getting bound before its first use. I then changed that without thinking in D8786 so we passed a `None` value into the function, which made it break in another way (trying to iterate over `None`). Then I tried to fix it up in D8810, but I only changed `hgwebdir_mod.py` for some reason, and it still doesn't actually work in frozen binaries (which seems fair, since was broken before my changes too). This patch just replicates the half-assed "fix" from D8810 in `webcommands.py`, so they look more similar so I can start refactoring them in the same way. Differential Revision: https://phab.mercurial-scm.org/D8933