contrib: make editmergeps use -NoNewWindow option in Start-Process cmdlet Running 'Start-Process -Wait "vim" "+10" "filename"' from PowerShell actually spawns a separate cmd window to run vim in. This looks ugly and in most cases not what user wants. During my initial testing I was using the Cmder app, which made me not notice this (it captures new windows as new tabs).

contrib: run editmergeps.ps1 from the same location as editmergeps.bat This change is needed for cases when user does not put editmergeps.bat directly into PATH, but rather uses 'merge-tools.editmergeps.executable' config option to provide a full path to editmergeps.bat. In such cases, editmergeps.ps1 cannot be run simply by name, it needs a full path. In BATCH file %~dp0 stands for the directory in which the original file is located.

help: pass commands module by argument This removes import cycle.

copies: introduce getdstfctx Previously `c2` may had an incorrect linkrev because getsrcfctx set wrong _descendantrev. getsrcfctx() sets descendant rev equals to srcctx.rev() (see _makegetfctx()), but for `c2` descendant rev should be dstctx. While we were lucky it didn't broke copytracing it made it significantly slower in some cases. Besides it broke some external extensions, for example remotefilelog.

copies: rename getfctx to getsrcfctx In the next patch we'll use getdstfctx. Let's rename getfctx to getsrcfctx in this patch.

copies: remove msrc and mdst parameters This function already has lots of parameters. And we can get manifests from contexts. So let's get msrc and mdst parameters from srcctx and dstctx.

copies: add dstctx parameter Add parameter with destination context

copies: rename ctx to srcctx In the next diff we'll pass new dstctx parameter. Let's rename ctx to srcctx in this patch.

copies: rename m2 to mdst Small refactoring to rename m2 to more clearer mdst.

copies: rename m1 to msrc Small refactoring that renames `m1` parameter name to a more clearer name `msrc`.