Git: Merge Branch... picker duplicates branch name in description (fix #199562)

[gjsjohnmurray]

This PR fixes #199562

Initially created as draft while we discuss what data (if any) to use as description.

[gjsjohnmurray]

Initial push replaces duplicated name with last commit timestamp:

As currently implemented this causes a noticeable delay while timestamps are fetched. Perhaps this can be improved by adding these lazily to the QuickPickItem description properties

Other ideas:

Commit ID (short format)

I think both of the above would benefit from #75835 (support for right-justfified descriptions in quickpick lists) being implemented.

Nothing
This is is what Rebase does for most of its entries. There the exception is the upstream entry, for which description gets set to '(upstream)'

[lszomoru]

@gjsjohnmurray, thanks for your contribution. Ideally, we would want all brach pickers should be consistent. Could we have this one look like the branch picker that is being shown when you invoke the "Checkout" command? Thanks!

[gjsjohnmurray]

[gjsjohnmurray]

Can this get merged soon, or do the rules of your grooming iteration mean it'll have to wait another month?

[lszomoru]

@gjsjohnmurray, thank you very much for the pull request. I took the liberty to build on top of this to distinguish local and remote branches. Closing this PR in favour of #200331.