Straighten graph lanes

[mstv]

Fixes #5782

Proposed changes

• Move lanes to the right if a branch would go to one lane left for one row
• Use array instead of List<RevisionGraphRevision> in RevisionGraph

Screenshots

Before

After

Test methodology

• manual

Test environment(s)

• Git Extensions 33.33.33
• Build b737b53
• Git 2.27.0.windows.1 (recommended: 2.30.0 or later)
• Microsoft Windows NT 10.0.19042.0
• .NET Framework 4.8.4300.0
• DPI 96dpi (no scaling)

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✒️ I contribute this code under The Developer Certificate of Origin.

[mstv]

Tests fail only on AppVeyor...

[gerhardol]

This is partly based on #5783

[RussKie]

Is there a way to unit test this?

[RussKie]

Suggested change

	RevisionGraphSegment[] segmentsToBeMoved = _segmentLanes.Where(keyValue => keyValue.Value >= fromLane).Select(keyValue => keyValue.Key).ToArray();
	RevisionGraphSegment[] segmentsToBeMoved = _segmentLanes.Where(keyValue => keyValue.Value >= fromLane).Select(keyValue => keyValue.Key);

[mstv]

This is not an iterator of the C++ std lib, which allows the modification of values.
Without, it throws InvalidOperationException "Collection has changed".

[mstv]

Is there a way to unit test this?

Yes, there is. I agree and will add tests for RevisionGraphRow.MoveLanesRight.

The algorithm for StraightenLanes in RevisionGraph.BuildOrderedRowCache is pretty straightforward.
The screenshot in the issue description #5782 and the comment in the function describe the simple but powerful idea.
Though a test would need extensive mock-ups.

My implementation - with moving all lanes right - avoids that independent branches use the same lane as in #5782 (comment).
Furthermore, it is important that the segments are processed in the order they have been added, not in the necessarily different order when the segments are drawn.

[mstv]

I have rebased and improved the performance. AppVeyor builds finish in normal time.

[RussKie]

Haven't run

[mstv]

@msftbot merge in 3 days

[ghost]

Hello @mstv!

Because you've given me some instructions on how to help merge this pull request, I'll be modifying my merge approach. Here's how I understand your requirements for merging this pull request:

• I won't merge this pull request until after the UTC date Wed, 31 Mar 2021 20:50:24 GMT, which is in 3 days

If this doesn't seem right to you, you can tell me to cancel these instructions and use the auto-merge policy that has been configured for this repository. Try telling me "forget everything I just told you".