Tweak and fix the update footer

[yubiuser]

What does this PR aim to accomplish?:

1. Do not propagate the update status from one component to the next. Reset the variable
2. Don't link to the release page when not on master but to the commit history
3. Fix the how-to-update footer
4. Don't assume there is an update when remote hash is empty (happens on custom branches when the remote branch gets deleted)

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[yubiuser]

Maybe someone can test if everything works as expected on docker?

[rdwebdesign]

I saw a small visual detail:

We could add a space before the · character (line 545).

[yubiuser]

I added a &nbsp