[PATCH v7 0/3] graph: indent visual roots in graph

[Pablo Sabater <pabloosabaterr@gmail.com>]

When rendering a graph, if the history contains multiple "visual roots",
actual roots or commits that look like roots (i.e. have their parents
filtered out) can end up being vertically adjacent to unrelated commits,
falsely appearing to be related.

A fix for this issue was already attempted [1] a while ago.

This series adds indentation to the visual root commits, so they cannot be
vertically adjacent anymore making it easier to identify them.

Before indentation:

	* A
	* B1
	* B2
	* C1
	* C2

After indentation:

	  * A
	* B1
	 \
	  * B2
	* C1
	* C2

Indents the visual root commits that have still commits to show after
them, and if they have children it connects them with an edge at a new
row.

If there are multiple visual roots adjacent in history, the indentation
starts with the second one, avoiding redundant indentation of the first
one and cascades after the second.

	* A
	  * B
	    * C
	* D1
	* D2

This series first commit is a cleanup that brings a common function
from t4215 and t6016 to a graph functions file which they both use, so
the new test file for indentation, t4218, can use it as well.

[1]: https://lore.kernel.org/git/xmqqwnwajbuj.fsf@gitster.c.googlers.com/

V6 DIFF:

- Replaced the queue peeking with a 2-entry lookahead buffer populated by
  get_revision_internal() (second commit and graph_peek_next_visible()).

- Changed assert() with BUG() at graph_output_pre_root_line().

Signed-off-by: Pablo Sabater <pabloosabaterr@gmail.com>
---
Pablo Sabater (3):
      lib-log-graph: move check_graph function
      graph: add a 2 commit buffer for lookahead
      graph: indent visual root in graph

 graph.c                                    | 282 ++++++++++++++++++
 graph.h                                    |  17 ++
 revision.c                                 |  17 +-
 t/lib-log-graph.sh                         |   5 +
 t/meson.build                              |   1 +
 t/t4215-log-skewed-merges.sh               |  33 +--
 t/t4218-log-graph-indentation.sh           | 453 +++++++++++++++++++++++++++++
 t/t6016-rev-list-graph-simplify-history.sh |  25 +-
 8 files changed, 798 insertions(+), 35 deletions(-)
---
base-commit: e9019fcafe0040228b8631c30f97ae1adb61bcdc
change-id: 20260612-ps-pre-commit-indent-39ca72816382

Best regards,
--  
Pablo Sabater <pabloosabaterr@gmail.com>