convert: introduce hascommitfrommap sink method Mercurial has stable revision identifiers and rollback and strip. Revisions referenced in the shamap are thus not necessarily still present but we can easily check for it. Subversion do not have stable identifiers and no rollback or strip(?). We must thus assume that all revisions referenced from a shamap still must be present. This method is similar to hascommitforsplicemap but different ...

convert: rename sink hascommit to hascommitforsplicemap The name 'hascommit' sounds like something generic ... but it might also throw exceptions in specific cases and it is thus (apparently) only useful for splicemap.

tests: better tests for two-way convert

mergetools.hgrc: add minimal configuration for editmerge The ``editmerge`` script is shipped in contrib and opens an editor on every conflicting file. It needs minimal configuration to inject the config marker in the file before opening. Otherwise it behaves the same as ``internal:local`` and bad things happen.

merge with stable

convert: drastically speed up git conversions We would formerly exec git cat-file once for every commit, plus once for every tree and file we wnated to read. This switches to using git cat-file's batch mode, which is much, much, much faster. Using this new code, converting the git git repo to hg ran in 106 minutes on my machine. Using the stock mercurial, it required 1239 minutes. I believe this to be typical of the speedups we will see form this patch.