This a draft PoC. I wanted to know whether it is worth the effort to smooth the kinks or whether I rather should not bother you with this again.

+1 from me
Have been using this occasionally too.

I wanted to know whether it is worth the effort to smooth the kinks or whether I rather should not bother you with this again.

We all have likes and dislikes :) And if others like this way better - we'll have it, especially since there's an option to turn it off.

Any progress?

yes, @xnousnow

Before / After

Are these reflecting the latest state?

Are these reflecting the latest state?

Yes, they are. The drawing of the graph is ready for review.
(In a follow-up, I am going to turn multi-lane crossings into "diagonals": 13776d6. This is done in the same lower layer as #10778. I.e. it is an independent change.)

Open points (not affecting the graph):

• Avoid often instantiation of SegmentDrawer perhaps as in a44f5a8? Code smell "static instance" though.
• AppSettings.ReduceGraphCurves to be added to a settings page?

We probably should move all graph related settings on their own dedicated page but in a separate PR :)

@mstv Can the verify.txt files be renamed to be shorter?

Because there is for example the file UnitTests\GitUI.Tests\UserControls\RevisionGrid\Graph\RevisionGraphTests.UnfoldOneLaneShiftsToDiagonals_commitSpecs=0-D,1,2,3,4,5,6,B,8,9,7 1-D 2-D 3-E 4-E 5-C 6-C 7-G 8-9 9-A A-B B-C C-F D-R E-F F-R G-H H-R R.verified.txt which is 223 characters long and it will be painful for everyone to handle (and especially the new contributors as I think that cloning will probably fail).

As a consequence, I can't do anything with master due to error:

error: cannot stat 'UnitTests/GitUI.Tests/UserControls/RevisionGrid/Graph/RevisionGraphTests.UnfoldOneLaneShiftsToDiagonals_commitSpecs=0-D,1,2,3,4,5,6,B,8,9,7 1-D 2-D 3-E 4-E 5-C 6-C 7-G 8-9 9-A A-B B-C C-F D-R E-F F-R G-H H-R R.verified.txt': Filename too long

Can the verify.txt files be renamed to be shorter?

I am the wrong addressee. I have not pursued the switch to it (and I am not 100% convinced of it. E.g. comments cannot be added in place).

which is 223 characters long and it will be painful for everyone to handle

Which kind of problems other than MSYS Git issues? I have never noticed any - and I have rebased these commits many times and have checked them out on a few machines. Though in my checkout, the pathname does not exceed 260 characters.
Perhaps git config --global core.longpaths true helps (refer to https://stackoverflow.com/questions/22575662/filename-too-long-in-git-for-windows)

I can the see the point of renaming this test, it is long and can cause some issues.
Verify tests allow customisation of the test names. I'd go with https://github.com/VerifyTests/Verify/blob/main/docs/naming.md#testclassname, e.g. something like:

        [Test]
        [TestCase("0:1,4 1:2 2:R,3 3:R 4:R R", "case1")]
        [TestCase("0:1,R 1:2,R 2:4,3 3:R 4:5,8 5:6 6:7,R 7:R,R 8:9 9:R R", "case2")]
        [TestCase("0:D,1,2,3,4,5,6,B,8,9,7 1:D 2:D 3:E 4:E 5:C 6:C 7:G 8:9 9:A A:B B:C C:F D:R E:F F:R G:H H:R R", "case3")]
        [TestCase("0:4 1:3,2 2:6 3:8,B 4:5 5:A,6 6:7 7:8 8:C,R 9:A A:B,R B:R C:R R", "case4")]
        public async Task UnfoldOneLaneShiftsToDiagonals(string commitSpecs, string testNameSuffix)
        {
            AppSettings.StraightenGraphDiagonals.Value = true;

            RevisionGraph revisionGraph = CreateGraphTopDown(commitSpecs);

            await VerifyGraphLayoutAsync(revisionGraph, $"{MethodBase.GetCurrentMethod().Name}_{testNameSuffix}");
        }

        private static async Task VerifyGraphLayoutAsync(RevisionGraph revisionGraph, string testNameSuffix)
        {
            string actualGraph = AsciiGraphFor(revisionGraph).Join("\n");
            await Verify(actualGraph)
                .UseMethodName(testNameSuffix);
        }

E.g. comments cannot be added in place

I'm not quite sure I follow, could you please elaborate?

E.g. comments cannot be added in place

I'm not quite sure I follow, could you please elaborate?

Comments like the following would benefit from having the ASCII graph in the code - but not in a dedicated file.

        // Do not move the right lane of row 2.
        [TestCase("0:1,5 1:2   2:R,3 3:R,4 4:R   5:R R")]
        // Do not move the right lanes of row 6.
        [TestCase("0:1,R 1:2,R 2:4,3 3:R   4:5,R 5:6   6:7   7:8,R 8:9 9:R R")]
        // Do not move the right lanes of row 4.
        [TestCase("0:1,R 1:2,R 2:4,3 3:R 4:5,8 5:6,R 6:7,R 7:R,R 8:9 9:R R")]
        // Do not move segment 4:8 at row 6 & 5.
        [TestCase("0:5,1,2,3,4 1:5 2:5 3:6 4:8 5:R 6:7 7:8,B 8:9 9:R,A A:R   B:R     R")]
        // Do not move segment 7:B at row 9.
        [TestCase("0:5,1,2,3,4 1:5 2:5 3:6 4:8 5:R 6:7 7:8,B 8:9 9:R,A A:R,C B:R C:R R")]

Though since I do not expect many further changes to the graph rendering, this does not matter very much.

While adapting #11594, a file was created which exceeded the 260 characters limit.
git config --global core.longpaths true indeed made git clean work again.