Enable hunk staging mode by default

[stefanhaller]

• PR Description

In #4684 we improved the hunk selection behavior to work on blocks of changes instead of actual hunks, and I find this so useful that I wanted to use it by default. In #4685 I added a user config to make hunk selection the default, but I made it an opt-in config because I was worried that users might not find out how to switch back to line selection if needed.

To address this concern, in this PR I add a popup that explains this the first time the user enters staging; there is also a breaking changes notice at startup, and we improve the options display at the bottom of the screen to be clearer about this. Hopefully these measures are enough to not confuse people.

Closes #4759.

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for 98801da1	✅ 86.42%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (98801da)	Report Missing	Report Missing	Report Missing
Head commit (c216388)	57205	49714	86.90%

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#4780)	81	70	86.42%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

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[lonix1]

@stefanhaller Just upgraded and it showed me that little "popup" stating to change useHunkSelectionMode if I want the old behaviour. That seems incorrect, and I couldn't find it in the docs, but did find useHunkModeInStagingView. I assume that is the correct one.
UPDATE: there was another popup, and that one shows the correct setting key.

[stefanhaller]

@lonix1 Ah damn, you are quite right, that's a typo. Fixed in #4800.

Too bad that you reported this only a few hours after I released the 0.54.1 hotfix, would have been nice to include it there. I'm not sure it's worth making another point release now just to fix that text.

Also, my hope is that most people won't actually use the config and go with the new default instead, which I strongly believe is better for most situations.

[lonix1]

I like the new feature, but I prefer the old way of line-by-line in many cases. I have my finger on the "a" key and toggle it based on what I'm committing. For a large hunk where I know what's inside, it's very useful - and will save my keyboard from failing due to me mashing the space key like it's a videogame! 😆