Use `GitHub.OpenFromUrl <url>` from the VS Command Window to clone a
target URL. This spike uses existing `ShowReCloneDialog` method.

Expect Owner="github", RepositoryName="VisualStudio" from:
https://github.com/github/VisualStudio/blob/master/README.md

Not Owner="master", RepositoryName="README.md"

Only files on master branch are currently supported.

Trim line number when using FindPath.

Prototype this using the happy path where we use the default repository
location.

If we're already in an appropriate context, simply open the target file.

The following URL will now have an owner of "owner":
https://github.com/owner
Previously it would make a repository name of "owner".

Add code to parse window titles and find the GitHub context from the
topmost Chrome browser.

If there is no URL in the paste buffer, use the GitHub context from the
topmost browser.

When browser is in the context of a file, open a file with the same
name after repository is opened.

OpenFromUrlCommand now works with GitHubContext objects rather than
directly with URLs.

Visual Studio line numbers are zero based.

Assume that branch names don't contain a '/' (sic).

Navigate to line when line number information is available.

Search for Chrome then Firefox windows.
Need to find a way to search in order of height.

Previously highlighting only worked when a range was selected.
Use VsShellUtilities.OpenDocument instead of
DTE.ItemOperations.OpenFile.
Factor TryOpenFile into GitHubContextService.

Don't continue to column 0 on the line below.

GitHub URLs combine branches/SHAs and tree paths.

For example:
https://github.com/github/visualstudio/tree/master/src

Git would represent "master/src" as the tree-ish "master:src". Because
looking at the URL we don't know where the branch stops and the tree
starts, "master/src" is being stored as the TreeishPath property.

This enables round tripping between `Copy link to clipboard` and `Open
from GitHub`.

This is a mirror of `GitHub.CopyLink`.

Check that object exists before navigating.

Currently doesn't support opening/cloning repo so show message instead.

Interface shouldn't depend on LibGit2Sharp and return stale GitObject.

This will let us give user more meaningful warnings.

Warn if there have been chances to the target file between when the
permalink was created and the working copy.

We don't want to navigate to a stale source file, so show the original
blob using the AnnotateFile view.

This method only knows how to resolve blobs (not commits or trees).

Everything now uses ResolveBlob.