Context locking

[smashwilson]

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Description of the Change

Restores the behavior of following the WorkdirContext associated with the active pane item. Introduces the concept of a "locking" a WorkdirContext, so that one chosen explicitly from a context tile can be preserved even as you navigate elsewhere. Adds a padlock icon to the context tile to control toggling the lock.

Hat tip to @jarvelov for the locking idea! Solves a tricky UX problem in an elegant way.

Remaining work

• Introduce context locking in GitHubPackage
• Restore active pane following in GitHubPackage
• Drill context lock state and context lock manipulation callbacks into the git and GitHub tab react trees
• Implement context lock toggling action in the appropriate controllers
• Add the context lock toggle control to the context tile views
• Find an SVG editor and edit the lock octicon to make an unlocked svg icon.
• Actually run the code and fix the inevitable bugs 😄
• Tests passing and full change coverage

Screenshot/Gif

Alternate Designs

See #2335 for an extended discussion about this.

Benefits

This will allow us to preserve the benefits of having visibility of, and explicit control over, the current WorkdirContext, while reintroducing the convenience of the context following active workspace items.

Possible Drawbacks

It will still be possible for users to get lost if they do something like open a file outside of their working repo for a quick configuration edit; see #1595 for some of this confusion. With this change, they will be able to lock their context to prevent this from happening, but if they aren't already working across multiple projects

Applicable Issues

Fixes #2335.

Documentation

N/A

Release Notes

• Git repository context may be "locked" to manage manually or "unlocked" to follow the active pane item.

User Experience Research (Optional)

N/A

[codecov]

Codecov Report

Merging #2399 into master will decrease coverage by 0.07%.
The diff coverage is 97.58%.

@@            Coverage Diff             @@
##           master    #2399      +/-   ##
==========================================
- Coverage   93.43%   93.35%   -0.08%     
==========================================
  Files         235      235              
  Lines       13066    13147      +81     
  Branches     1859     1885      +26     
==========================================
+ Hits        12208    12274      +66     
- Misses        858      873      +15

Impacted Files	Coverage Δ
lib/controllers/github-tab-controller.js	100% <ø> (ø)	⬆️
lib/views/git-tab-view.js	86.36% <ø> (-0.16%)	⬇️
lib/controllers/git-tab-controller.js	80.67% <ø> (ø)	⬆️
lib/views/github-tab-view.js	100% <ø> (+4.54%)	⬆️
lib/controllers/root-controller.js	83.78% <ø> (ø)	⬆️
lib/atom/octicon.js	100% <100%> (ø)	⬆️
lib/controllers/github-tab-header-controller.js	100% <100%> (ø)	⬆️
lib/controllers/git-tab-header-controller.js	100% <100%> (ø)	⬆️
lib/views/github-tab-header-view.js	100% <100%> (+7.69%)	⬆️
lib/containers/github-tab-header-container.js	100% <100%> (ø)	⬆️
... and 5 more

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[wadethestealth]

Looking pretty good so far! 👍

[smashwilson]

Thanks! ✨

Just need to get the "unlock" icon looking right, then write the hover copy for the lock button states, I think.

[aviatesk]

Thanks for your work, @smashwilson ! Looking forward to giving a try on this !

[jarvelov]

Awesome work @smashwilson! 🎉

[mordash]

Awesome ! thanks

[pouruthi]

I