Re: [GSoC RFC PATCH v2 0/1] graph: add indentation for commits preceded by a parentless commit

>
> When having a history with multiple root commits or commits
> that act like roots (they have excluded parents), let's call
> them parentless, and drawing the history near them, the
> graphing engine renders the commits one below the other, seeming
> that they are related.
>
> e.g.:
>
>   * parentless-B
>   * child-A2
>   * child-A1
>   * parentless-A
>
> This issue has been attempted multiple times:
>   https://lore.kernel.org/git/xmqqwnwajbuj.fsf@gitster.c.googlers.com/
>
> This happens because the engine prints left to right from the first free
> column and these parentless commits for the next row, their column
> becomes empty and the engine fills that gap with the next commit (child-A2)
> seeming that parentless-B and child-A2 are related when they are not.
>
> The actual implementation is very minimal.
> This patch makes the parentless commits to be kept alive at least one more row to avoid
> that, indenting the next commit to the next column and then clean the mapping
> letting the indented commit to naturally collapse to the column where the
> parentless commit was.
>
> e.g.:
>
>   * parentless-B
>     * child-A2
>    /
>   * child-A1
>   * parentless-A
>
> This is done by adding a is_placeholder flag to the columns, the parentless
> commit is actually there but marked as a placeholder
>
> e.g.:
>
>    * parentless-B
>   (B) * child-A2
>     /
>    * child-A1
>    * parentless-A
>
> (B) would be parentless-B column with the placeholder flag active.
>
> By teaching the rendering function to print a padding ' ' when meeting a
> placeholder column hides them, printing the second example.
>
> There could also be the case where there are multiple parentless commits
>
> without the patch:
>
>   * A parentless
>   * B parentless
>   * C parentless
>   * D1 child
>   * D parentless
>
> with the patch, the indentation cascades:
>
>   * A parentless
>     * B parentless
>       * C parentless
>         * D1 child
>      _ /
>     /
>    /
>   * D parentless
>
> the _ / might look weird but that's how the collapsing rendering does it
> for big gaps, this case being from the 4th column to the 0th column.
>
> Another patch could change the collapsing rendering for placeholders?
> I haven't done it to keep it minimal, but a follow up could make it
> to be straight '/'. This would make it bigger but easier for the eye to follow.
> IMO is not worth it, but opinions are welcome.
>
> The patch also adds tests for different cases like a parentless commit
> preceding multiple parents merges and the examples above.
>
> There could be some edge cases still so any testing is very welcome.
>
> PSA: the tests are on t4215-log-skewed-merges.sh, which is not very related,
>      but other graph related tests have +140 tests, and this one has less than
>      20 and some of them are also not very related and differ in style.
>      A cleanup patch before this renaming the file and style of the tests is fine?
>
> Changes from v1:
>
> - Changed to parentless commits instead of root commits to make it more generic
> - Fixed the branch names to pass CI and fixed tests style.
>
> Pablo Sabater (1):
>   graph: add indentation for commits preceded by a parentless commit
>
>  graph.c                      |  70 ++++++++++++++++++--
>  t/t4215-log-skewed-merges.sh | 124 +++++++++++++++++++++++++++++++++++
>  2 files changed, 188 insertions(+), 6 deletions(-)
>
>
> base-commit: 8de2f1b07a8053d7f1aad70dc1131d6afcf5a28a
> --
> 2.43.0
>