This is a MVP implementation of open file from GitHub functionality.

With this functionality the user can paste a /blob/ style URL into the URL tab of the Open from GitHub dialog and be taken to the file/line/range after the target repository is opened or cloned.

When the target /blob/ isn't available in the working directory, a dialog will appear letting the user know about the problem. There is no functionality to assist navigation to an alternative remote branch or pull request (if that is where the /blob/ URL is from).

This functionality isn't advertised/discoverable and will be primarily used for gathering user feedback and testing when the functionality is explicitly pointed out.

Scope of MVP

• Support https://github.com/owner/repo/blob/<branch>/<path>/<file> style URLs
• Support https://github.com/owner/repo/blob/<SHA>/<path>/<file> style URLs
• Support navigation to individual lines or ranges (e.g. URL ends with #L10 and #L25-L33)
• Open any file that hasn't changed on the current branch
• Show dialog if target file can't be found in local repository
• Show dialog if working directory file is different to target file

Next iteration

• Advertise functionality on Open from GitHub / URL page
• Find pull request associated with permalink-URLs
• Find remote branch associated with permalink-URLs
• Automatically fetch when target file can't be found in local repository
• Offer to open pull request when permalink points to a pull request file
• Offer to checkout branch when link points to a remote branch

What this PR does

• Bring together the Open from GuitHub and Open from Clipboard functionality
• Always show URL tab of Open from GitHub dialog when there is a GitHub URL in the clipboard
• Add .GitHubContextService.TryNavigateToContext for syncing Visual Studio context with context from a /blob/URL
• Show warning dialog when working directory file is different to file pointed at by /blob/ URL
  • This can be established using the commit SHA or permalink URLs and the latest fetched commit of remote branches
• Show warning dialog when file pointed at by /blob/ URL doesn't exist in local repository
  • This dialog is more helpful when the remote branch name is included in the URL (the more common case when browsing GitHub)
  • Then the /blob/ URL is a permalink, we don't currently know the remote branch/PR it is associated with

Notes and Issues

• When a user opens a blob permalink, we don't know the name of the branch they're targeting

  • I've been prototyping a solution for this issue here: https://github.com/jcansdale/GitPullRequest/

• When a user opens a blob from a named branch, files on the current branch might be different to the target branch

  • The current implementation compares the working file with the remote branch version

• If the user hasn't recently done a fetch, the targeted commit might not exist or the link might be out of date (if it uses a named branch)

  • The current implementation doesn't automatically do a fetch. A future version should automatically fetch if the file can't be found.

• When a range of lines is selected and a solution is opened using Team Explorer - Home, the selected text is lost but the caret position remains the same

  • When selecting a range, we have the option to start the selection at the top or the bottom. The current implementation starts at the top, which means the caret is left at the bottom of the range when the solution opens. I think this might work better if we start the selection at the bottom, leaving the caret at the top of the range. My guess is that the top position of a range is generally more important.
  • This would be a nice refinement, but isn't currently implemented

Discoverability

This feature isn't being advertised in the MVP

With this new functionality a user can paste a blob style URL into the Open from GitHub dialog and have the target file and line number/range selected as soon as the clone or Open completes. We need to find a way to make this functionality discoverable.

Currently is a user copies a blob style URL into their clipboard clicks File > Open > Open from GitHub..., they will be presented with this:

If there is no URL in the clipboard, they will see this:

• There is plenty of space below the repository field to let the user know what kind of URLs and shortcuts are supported here
• There is also the possibility of showing elements of the deconstructed URL (owner/repo/branch/line number/range)
• We could even check the repository exists and fetch its description

For the MVP I think it would make sense to work on these incrementally. Start off with a static description and only show elements of the deconstructed URL if they're deemed to be particularly useful.

What do you think @donokuda?