v0.19.0-0 QA Review #1638

QA Review to prepare for the v0.19.0 release. Let's build Atom with the v0.19.0-0 prerelease version of this package and ensure that all of the bugs we wanted to fix are fixed properly, and that there are no unexpected complications from snapshotting or asar-bundling.

The work we're testing can be found in the merged column of the project board for this sprint.

Checklist

• Use my fork of atom-mocha-test-runner #1637 - There should be no npm audit findings from dependencies of atom/github.
• PR meta infos #1607 - PR Meta Infos
• Undoing the first commit in a repository throws an exception #1440 + Undo an initial commit #1635 - Undo an initial commit
• Uncaught (in promise) TypeError: Cannot read property 'getLines' of undefined #1241 + Don't attempt to stage or unstage with no selection #1634 - No exception when using context menu to stage or unstage with no selection
• Should not display mode change for added file that is executable #1312 + Don't detect executable mode changes on added or deleted files #1633 - No "mode change" banner on file patches for added or deleted executable files
• Uncaught TypeError: Cannot read property 'dispatchEvent' of null #1229 + Detached DOM nodes have no parents #1632 - Discarding rapidly from the staging view throws an exception
• Remove "(preview)" from GitHub tab title #1602 - No "preview" in GitHub tab
• Uncaught TypeError: Cannot read property 'rememberFocus' of null #1490 + Prevent race conditions in focus management code #1631 - No stack traces from focus restoration code
• Activating dock no longer focuses git tab element #1614 + Activate the git tab on item activation #1629 - Focus the Git tab when activating the right dock
• More links to .com #1589 - Additional links to .com from PR detail panes
• Restyle hovercards II #1601 - Restyled hovercards on PR detail panes
• 🐛 Fix default dir for git repo init #1627 - Clicking the "init" button in the Git tab should default to the current working directory
• ✅ from CI in :arrow-up: github on dev atom#17831