fixes #8590

* Added `getLog` method to `Repository`.
  * Added `ILogOptions` to make the method friendlier to extension.
  * Options include `prevCount` and `format`, to effect our use case which is `git log -1 format=%B`.
* Added this to the client-server communication pipeline.

fixes #7830

* Cleaned up and corrected changeView calling code to avoid initial git commit msg stuff.
* Refactored `lastCommitMsg` to `prevCommitMsg` in pipeline.

* Added `getCommitInfo` to git `IModel`.
  * Added commitInfo to Model implementation class.
* Changed `IRawGitService.getCommitInfo` to return `IRawStatus` instead of `ICommitInfo` directly.
* Changed `IGitService.getCommitInfo` to return `IModel`.
  * This was required because it expects a status when performing a git operation from the client (not really documented nor obvious).

* Added `Repository.getLog(ILogOptions)` for getting the previous commit msg, but allowing extensibility.
  * Added `ILogOptions` with single `prevCount` for extensibility of other use cases when executing `git log -1` (which gets the previous commit msg).

InProgress:

* Implementing getCommitInfo to parse possible template file, as well as parse the previous log message.

fixes #3385

fixes #5974

fixes #4214

fixes #1539

# Conflicts:
#	src/vs/languages/html/common/htmlTags.ts

fixes #907
related to #150