Fix commit hash colors when filtering by path or aythor

[stefanhaller]

• PR Description

Previously we would call git merge-base with the upstream branch to determine where unpushed commits end and pushed commits start, and also git merge-base with the main branch(es) to see where the merged commits start. This worked ok in normal cases, but it had two problems:

• when filtering by path or by author, those merge-base commits would usually not be part of the commit list, so we would miss the point where we should switch from unpushed to pushed, or from pushed to merged. The consequence was that in filtering mode, all commit hashes were always yellow.
• when main was merged into a feature branch, we would color all commits from that merge on down in green, even ones that are only part of the feature branch but not main. (See Commit hash color incorrect after merge with main #3796)

To fix these problems, we switch our approach to one where we call git rev-list with the branch in question, with negative refspecs for the upstream branch and the main branches, respectively; this gives us the complete picture of which commits are pushed/unpushed/merged, so it also works in the cases described above.

And funnily, even though intuitively it feels more expensive, it actually performs better than the merge-base calls (for normal usage scenarios at least), so the commit-loading part of refresh is faster now in general. We are talking about differences like 300ms before, 140ms after, in some unscientific measurements I took (depends a lot on repo sizes, branch length, etc.). An exception are degenerate cases like feature branches with hundreds of thousands of commits, which are slower now; but I don't think we need to worry about those too much.

Fixes #3796.

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
Report missing for a02f1e81	✅ 94.03%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (a02f1e8)	Report Missing	Report Missing	Report Missing
Head commit (e46dc1e)	57211	49737	86.94%

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 (#4789)	67	63	94.03%

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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